Title: The Meaning of Evolution
Author: Schmucker, Samuel Christian, 1860-
Language: English
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THE MEANING OF
EVOLUTION

BY

SAMUEL CHRISTIAN SCHMUCKER, PH.D.

PROFESSOR OF BIOLOGICAL SCIENCES IN THE
WEST CHESTER STATE NORMAL SCHOOL
WEST CHESTER, PA.

[Illustration]

The Chautauqua Press
CHAUTAUQUA, NEW YORK
MCMXIII



COPYRIGHT, 1913
BY THE MACMILLAN COMPANY


Set up and electrotyped. Published June, 1913



CONTENTS


    CHAPTER                                             PAGE

            A FOREWORD                                     1

         I. EVOLUTION BEFORE DARWIN                        7

        II. DARWIN AND WALLACE                            21

       III. THE UNDERLYING IDEA                           44

        IV. ADAPTATION FOR THE INDIVIDUAL                 87

         V. ADAPTATION FOR THE SPECIES                   125

        VI. LIFE IN THE PAST                             149

       VII. HOW THE MAMMALS DEVELOPED                    192

      VIII. THE STORY OF THE HORSE                       220

        IX. EVOLUTION SINCE DARWIN                       233

         X. THE FUTURE EVOLUTION OF MAN                  249

        XI. SCIENCE AND THE BOOK                         274

    INDEX                                                293

    APPENDIX                                             299



A FOREWORD


Before my window lies an enchanting landscape. It embraces a stretch
of open rolling country, beautiful as the eye could wish to rest upon.
The sun with its slanting rays is not giving it heat enough in these
winter months to make it blossom in its radiant beauty, but the mind
goes easily back through the few brown months to the time when the
field not far away was waving with its rich yellow grain so soon to be
food for those who planted it. Beyond this field lies an orchard
where, in regular and orderly rows, stand the apple trees whose bright
blossoms in the spring make the landscape so beautiful and whose fruit
in the fall serves so richly for our enjoyment. A little farther on, a
pasture is filled with sleek-coated cows, feeding quietly and
patiently until the evening when they will return to their stalls to
yield their rich milk. Still farther on lies a tract of forest. The
varied shades of the beeches, the tulip poplars and the chestnuts make
an exquisite contrast and give to the landscape its attractive
background framed in by a distant hill. Behind this hill flows a
mighty river carrying on its breast the ships by which we share the
over-abundance of our own blessings with our brothers on the other
side of the sea, from whom in turn we receive of their overplus.
Beyond this teeming river lies a level stretch of fertile land and
then the mighty ocean. On one side of the scene runs a busy highway.
Along this men pass and repass, some on foot, others drawn by their
patient and submissive horses. Still others are carried by the
new-found power of the sunshine imprisoned beneath the rocks in the
oil that has been forming ever since the sun shone down upon the great
forests of the far distant past.

In a pathway to one side, some children are playing. One of them has
laid upon the ground a rectangle of stones divided into four and her
little mind sees before her the house which is teaching her to get
ready for the work that shall come to her in later life. Meanwhile her
short-haired companion is prancing around astride a stick; he too,
little as he suspects it, is getting ready for life.

It needs little reflection to realize that the scene has not always
been what it is. The underlying ground has surely been there longest,
its age vying only with that of the bounding ocean that beats upon the
shore and works the sand into fantastic stretches. The forest has been
there long and so has the stream; the road perhaps ranks next in age;
then come the orchard trees, and most recent of all the waving grain.
People come and go but form no stable part of this landscape. We know
how the grain came to be there, and we understand the orderly
arrangement of the orchard trees; the road too we can explain. How
came the stream there, and how the forest trees? Have they always been
there, or did they too have a beginning? Was there a time when there
was no ocean? When was this time? How came they there?

When the lisping lips of my young child asked me, "Papa, who made me?"
I told him "God," and he knew enough and was content with his
knowledge. After a while he grew older and his inquisitive spirit
began to puzzle with the question of how God had made him. When his
growing mind was ready for the new knowledge I took him to my side and
told him the great mystery of life. I told him how he owed to his
father and to his mother the beginnings of his life, how God gave him
to us. Now a new era opened in his childish mind. As he grows on to
greater maturity he cannot help wondering how the first man was made,
how the trees, and the world came to be. He is no longer satisfied
with the simple statement that God made them. His eager mind wants to
know, if may be, how God made them.

So, in the distant past, in the childhood of our race, the question
was asked, "Who made us?" and the answer was "God." Men formed their
simple conception at that time of how He did it. As the centuries
rolled by and the children of men have learned from creation the story
of its origin a riper and richer knowledge has given them a broader
and finer conception. No less does the reverent student believe that
God created the earth, but he no longer thinks of God as working, as
man works. He no longer feels that it is impious to attempt to read
God's plan in His work; to see how this work has arisen, to see, if
may be, what there is ahead.

This is one of the tasks to which science is now giving itself. The
answer is uncertain and halting. A few things seem clear; others seem
to be nearly certain; of still others we can only say that for the
present we must be content with the knowledge we have. But if we take
the best we have and work over it thoughtfully and carefully, the
better will slowly come, and in time we shall know far more than we
now suspect. Meanwhile, it is the attempt of this book to give to
people whose training is other than scientific some conception of this
great story of creation. Without dogmatic certainty but without
indecision it tries to tell what modern science thinks as to the great
problems of life. It tries to describe the possible origin of animals
and plants, their slow advance, the length of their steady uplift, the
forces that brought it about. It tries to tell a little of the men
who have helped to develop the great idea of evolution, of the great
men who persuaded the scientific world of its truth, and of the later
minds that are modifying and enlarging the idea of the master
evolutionist. It tries to tell what science perhaps vaguely hopes as
to the future. What are we to be? Can we help the great advance?



The Meaning of Evolution



CHAPTER I

EVOLUTION BEFORE DARWIN


Ever since men have been able to think they must have puzzled out for
themselves some way of accounting for their own beginnings. Every
savage tribe with whom we have any intimate acquaintance has some
story that accounts for the origin of the tribe at least, and often
for the beginning of the world. These stories are handed down from
generation to generation and are scarcely questioned in the thought of
most men. In early Greece there was a succession of men whom the world
calls philosophers. These men thought earnestly and deeply on all
kinds of questions. Their method was not our method. The plan of
making a long series of observations, before coming to any conclusion,
was not the habit of their minds. They reasoned out on general
principles what seemed to them must have been the origin of the world.
It is not strange that among these should come, now and then, some one
who in some passage or other should show that there had come to his
mind at least a glimmer of the thought that was later to develop into
the great idea which the modern world calls evolution.

Among the earliest of these was Anaximander, who lived 600 years
before Christ. He thought that the earth was at first a fluid.
Gradually this fluid began to dry and grow thicker, and here and
there, where it thickened most, dry land appeared. When this dry land
had become firm enough to serve as his home, man came up from the
water in the form of a fish. Slowly and gradually the fish, struggling
about on the land, gained for himself the limbs and members he needed
for his new situation and developed into a man. After him other
animals came up in much the same fashion, then the plants, until the
whole world was clothed with its present inhabitants.

One hundred and fifty years later Empedocles announced a new thought.
He said that in the beginnings there were all sorts of strange,
incomplete, and misjointed monsters which swarmed upon the earth,
having sprung up out of the earth itself. Each was a chaos of the
limbs which afterward were to belong to other animals which needed
them more. Slowly and gradually an interchanging came about by which
appropriate limbs fastened themselves to the proper animals. The last
of these misjointed creatures is the one known as the centaur,
half-man--half-horse. After a while, when all the members had found
their proper places, the animals were complete. In one respect this
opinion foreshadowed our later idea. It suggested that the more
perfect animals had arisen out of the less perfect and that the change
came gradually.

Then came Anaxagoras, who was the first to believe that there was
intelligent design back of the creation of animals and of plants. He
thought there had originally been a slime in which were the germs of
all the later plants, animals, and minerals, mixed in a chaos. Slowly
order arose. Out of the mixture settled first the minerals forming the
earth, with the air floating above it, and above the air was the
ether. Out of the air the germs of plants settled upon the earth, and
vegetation covered the mineral floor. Then from the ether came the
germs of animals and of men. These settled among the plants and sprang
up into the animals of the world, as well as the people.

The greatest scientific thinker of early Greece was Aristotle. He had
lived by the seashore and knew better than any other man of his times
the exquisite seaweeds and the still more beautiful marine animals. He
was the first to think of them as a linked series, the higher
developing out of the lower under the pressure of what he called a
perfecting principle. Out of the inanimate rocks had sprung the marine
plants--the seaweeds. From these had developed first "plant animals"
like the sea anemones and the sponges. These grew attached to the
rocks, as plants do. With higher development came locomotion, with
ever-increasing energy. At last man arose, the crown of all creation.
Presiding over all this advance is the "efficient cause," God.
Aristotle rejected entirely the earlier ideas that any of this work
came about by chance. He was certain of the existence of plan and
purpose in the development.

Just a little before the time of Christ the Latin poet, Lucretius,
wrote a poem on "The Nature of Things." Here he describes how in the
early years the beginnings of things in small, disjointed fashion
moved about among each other at first in utter confusion, each trying
itself with the other. After many trials the proper members came
together. When they had been thus placed the warmth of the sun shining
down upon the earth helped the earth to reproduce the same sort of
creatures. So living things came up and flourished. The poem expresses
many beautiful ideas, but the underlying conceptions lack the unity
and grandeur that marked Aristotle's work, which later was the potent
influence in shaping men's minds. It died out after a while, only to
awake in the Renaissance with marvelous vitality, starting the world
to think afresh great thoughts that would not die, but would grow from
that time on with ever-widening scope.

Among the Jews and early Christians the stately and beautiful account
in Genesis sufficed for all the needs of minds fully occupied with
other questions. With the growth of philosophy among Christian minds
again came the need of a satisfactory solution. St. Augustine was
probably the greatest of the so-called "Fathers" of the church. His
mind was eminently philosophical, and he was learned in the writings
of the older Greeks. He believed the language of Genesis to mean that
in the beginning God planted in chaos the seed that afterward sprang
up into the heavens and the earth. He further says that the six days
of creation were not days of time, but a series of causes, and that,
in the order described as these six days, God planted in chaos the
various beginnings of things. These in the fullness of time sprang up
into the world as we know it now. The problem was not a question about
which the church cared to trouble itself, and with the oncoming of the
Dark Ages the whole matter dropped nearly out of the thoughts of men.

When the times began to lighten we find the schoolmen, among the
greatest of whom was Thomas Aquinas. Referring especially to the
authority of his master, St. Augustine, he says that it would be easy
mistakenly to believe that the author of Genesis meant to convey the
idea that on each of the six days certain acts of creation were
performed. It is quite evident, thinks Aquinas, that in those early
times God only created the germs of things and put into the earth
powers which should later become active. After the Creator had thus
endowed the earth he rested from the work, which proceeded to develop
under the influence of these first germs.

Nearly four hundred years later, when Europe had finally awakened out
of the deep and refreshing sleep in which it had fortunately forgotten
much of the past, a new era dawned and modern thought began.
Immediately men commenced to busy their minds with broader problems
than they had been discussing since the time of the Greek
philosophers. The hand of tradition, however, was heavy on them still.
They dreaded to run counter to authority, and did not dare think
unrestrainedly. Descartes shows us how we can understand things better
if we will imagine a few principles by which it will be easy to
account for things as they are. Then he carefully elaborates these
principles as they occur to him; but he has no sooner done so than he
takes care to add, "Of course, we know the earth was not made in this
way."

A little later the philosopher, Leibnitz, believed in an orderly
creation that had advanced by regular degrees, and that the lower
animals had thus developed into the higher. He adds interestingly that
there are probably on some other planets animals midway between the
ape and man, but that nature has kindly removed such animals from the
earth in order that man's superiority to the apes should be entirely
beyond question.

By the middle of the eighteenth century men had begun to think more
fearlessly. The great Emanuel Kant wrote in his younger and less timid
years, "The General History of Nature and Theory of the Heavens." The
great Newton had by his law of gravitation brought order into the
heavens. Kant looked longingly for a greater Newton, who should find a
similar unity in the animal world. He saw the wonderful likenesses
between animals that the anatomist, Buffon, had recently pointed out.
He believed there must somehow be blood relationship between all
animals. He tried hard to conceive of some underlying natural cause by
which all could have come about. As he grew older and his mind became
more cautious he came to think the matter deeper than the human mind
could ever fathom. He gave up the hope and believed the problem of
animal origin and derivation would forever remain insoluble. He
feared there was not in man the power to conceive his own origin.

If we ever wonder why it took so long before the thought of evolution
should have fully dawned upon the world, the answer is not far to
seek. No student of Natural History in ancient or medieval times had
the faintest conception of the enormous number of animals and of
plants in the world. The old Greek or Roman student of Natural History
gives no evidence of knowing more than a few hundred animals. Men have
named to-day, with systematic Latin names, hundreds of animals for
every one that Pliny ever knew, and he knew more than any other man of
early times of whom record has come to us.

In early days men who traveled into foreign countries brought back
accounts of what they saw. The whole Natural History of ancient times
was filled with the most absurd and ludicrous stories of all sorts of
things to be seen in distant lands. Sir John Mandeville tells tales
almost as imaginative and quite as amusing as those attributed to
Baron Munchausen.

Upon the great awakening of the fifteenth century, with its new study
and its wide-ranging travel, an entire change came over the human
mind. Men who journeyed into far countries brought back with them not
only accounts of what they saw, but, so far as might be, the things
themselves. Collections of plants and of such parts of animals as
could be readily preserved soon began to accumulate in every great
center of Europe. It was only a question of time when such
acquisitions must be arranged and classified, but as yet there was no
system by which this could be done. The great Swedish botanist,
Linnæus, who lived in the eighteenth century, first taught us to give
to each animal and plant two Latin names, the first of these to be the
name of the group, known as a genus, to which it belongs, the second
to be the name of that sort, or species, of animal. The cat, for
instance, is _Felis catus_, the lion _Felis leo_, the tiger _Felis
tigris_, and so on. Linnæus then arranged the genera (plural of genus)
into families, and these families into orders and so classified the
animal and plant world as far as he knew it. In his earlier years
Linnæus thought of each species as being utterly apart and distant
from any other. He believed it had been so from the first, each
species having sprung in its complete form from the creative hand of
God. In later life he came to show some evidence of the belief in
development, but his great work is all built on the idea of the entire
fixity of species.

About this time we find in the writings of Buffon, the French
naturalist, many indications of an idea approaching our modern
conceptions of evolution. He felt sure the pig could not have been a
special creation, because he had four toes, two of which, with all
their bones and their hoofs, are quite useless to him. We now call
these toes "vestigial," and know the pig's ancestors used them,
walking on four toes and not on two, as at present. Buffon believed
there were degenerations as well as developments, and considered the
ape a degenerate man. He conceived these changes to be brought about
by what he called the favors and disfavors of nature. He varied much
in his opinions in various parts of his career and occasionally is
smitten either with conscience or with fear of authority. Then he goes
back and says it is all a mistake and each animal is the product of a
special act on the part of the Creator.

A little later, in England, Erasmus Darwin, the grandfather of Charles
Darwin, who was subsequently to establish the evolution theory, wrote
a long and elaborate poem called the "Temple of Nature." In this we
find a remarkable prevision of many of the principles which were
afterward to be warmly advocated and disputed during the growth of the
idea of evolution.

    "Hence without parents by spontaneous growth,
    Rise the first specks of animated life.

        *    *    *    *    *    *    *

    Thus as successive generations bloom
    New powers acquire and larger limbs assume."

Erasmus Darwin recognized the struggle for existence, but he saw in it
only a check against overcrowding, and not an active factor in the
development as his grandson Charles came to see it. It is possible the
elder Darwin's views might have been taken more seriously had he not
clothed them with the form of verse. In these days it seems quite
ludicrous to think of giving to the world a new scientific concept or
a new phase of philosophy in verse.

The beginning of the nineteenth century gives us the first really
great contribution to the idea of evolution. Under more favorable
surroundings, this idea would have budded and become the parent stock
of our modern theories. The chill frosts of adverse criticism by those
in authority in science nipped the budding idea and so set it back
that only of late years have men come to realize its strength and
power. The Chevalier de Lamarck, serving in Monaco, was attracted by
its rich flora to the study of botany. Coming later to Paris, he
became acquainted with Buffon and was led by him to publish a Flora of
France, using the Linnæan system of classification. He was appointed
to the chair of zoölogy in the Jardin des Plantes, and was given
especial charge of the invertebrate animals, comprising all the
members of the animal kingdom except those with backbones. After
seventeen years of work over these forms, during which he wrote
several books describing them, he finally published the great work on
which his fame depends. This was the "Philosophie Zoölogique." In this
treatise he taught that the animal kingdom is a unit and that all its
members are blood relations; that the members vary with varying
conditions; that this variation results in continued advance. In all
of these points Lamarck is at one with modern thought. His idea of the
method by which the variation comes about has been accepted and
rejected; modified, reaccepted, and again rejected.

Lamarck's conception of the cause of progress was somewhat as follows:
The desire for any action on the part of an animal leads to efforts to
accomplish that desire. From these efforts came gradually the organ
and its accompanying powers. With every exercise of these powers the
organ and its corresponding function became better developed. Every
gain either in function or in organ was transmitted to those of the
next generation, who were thus enabled to start where their parents
left off. The general environment constantly gave the stimuli that led
to the adaptive changes.

American zoölogists have been especially inclined toward Lamarck's
ideas. Until Weissmann startled the scientific world with his sharp
denial of the possibility of transmitting to offspring any growth
acquired by the parents, all seemed well. There is a tendency now to
insist once more that slowly and gradually, in some perhaps as yet
unexplained way, external factors do influence even egg cells, and
gradually acquired characters do reappear in the offspring.

The blighting setback these views suffered came from the criticisms of
Baron Cuvier. This genuinely remarkable man had built up the study of
comparative anatomy. To him students flocked from all sides. Among
these one of the most brilliant was Agassiz, the Swiss naturalist, who
later came to this country, filled with Cuvier's ideas. This great
teacher believed that species are fixed. He knew better than any man
of his times the wonderful similarity in structure between animals of
a given class. He attributed this not to any real blood relationship
between the animals. They were alike because they had been made by the
same Creator. This great Artificer worked along four main lines, and
hence animals could be divided into four groups. Many who have studied
text books on zoölogy written in this country by Agassiz and his
followers will remember the four classes--Radiates, Articulates,
Mollusks, and Vertebrates. Agassiz was such a wonderful teacher and so
genial and so lovable a man that his opposition to evolution held back
the advance of the Darwinian idea in America as Cuvier's influence
had held back the Lamarckian idea in Europe. For the brilliant Cuvier
simply laughed before his students at each "new folly" of Buffon and
of Lamarck. Under this ridicule the influence of both men withered and
died.

A little later the great poet, Goethe, turned his attention to the
problem of evolution, giving an interesting account of the
metamorphoses of plants. He declared, also, that the human skull is a
continuation of the backbones of the neck, and that these bones have
been transformed into the present skull. But his great genius as a
poet drew his attention into other fields. Haeckel points out that if
Goethe had known Lamarck's work his genius would have gained for the
"Philosophie Zoölogique" the interest and respect of the reading
world. But Cuvier laughed it out of court, and only in comparatively
modern times, since Darwin's work has set the world thinking anew, is
Lamarck's career recognized at its true value. Lamarck should have
been the founder of the evolution theory. But the time was not quite
ripe, and it remained for Charles Darwin to announce his idea,
sustained and fortified by years of careful observation and thoughtful
reflection.



CHAPTER II

DARWIN AND WALLACE


We have seen in the last chapter that whenever men have actively
thought they have attempted to explain the origin of plants and
animals as well as of themselves. No one who wrote previous to the
time of Charles Darwin had expressed any idea concerning this matter
with force enough to convince any large portion of the thinking world.
If Lamarck had fallen on better times, if the great Cuvier had not
laughed him to scorn, if Goethe had found him out and made him known
to the world, evolution might have come into its own sooner. None of
these conditions arose, and it remained for Charles Darwin to give to
the world in clear and cogent form the thought of evolution. He
gathered so much material before he expressed his opinions, and looked
at the matter from so many sides that, when he published his results,
he had foreseen most of the objections which were subsequently to
arise in opposition to his announcement. Charles Darwin is recognized
to-day as the father of the evolutionary movement.

It has been sometimes said in recent years that Darwinism is dead, and
there is a sense in which this is true. Unmodified and unassisted
natural selection is not to-day considered by most scientists a
sufficient agent for producing evolution. But everyone connected with
the subject acknowledges Darwin as the master, and says that it was
his work which converted the world to a belief in evolution. We can
have no better preparation for an intelligent understanding of this
subject than to consider carefully the life of this remarkable man and
the circumstances under which he came to his epoch-making conclusions.

Evolution has taught us to attempt as far as may be to account for man
on the basis of his heredity or of his environment. It is interesting
to note that both of these factors in Darwin's case were entirely
favorable. In the latter part of the eighteenth century Erasmus Darwin
had given to the world an astonishing poem in which he anticipated not
a little of the thought which his more famous grandson was to make so
widely known. Josiah Wedgwood had learned to make for England her most
famous pottery, no quality of which was more widely recognized than
the sterling patience with which it was made. Erasmus Darwin, with his
scientific proclivities, and Josiah Wedgwood, with his sturdy common
sense and patient workmanship, united to give Charles Darwin his
inherited tastes, for he was a grandson of both. Born in 1809, on the
banks of the Severn in England, Charles Darwin was the delicate son of
a practicing physician of modest but sufficient means. Owing to his
lack of early vigor, Darwin spent much time in the open air, and in
his excursions about his home was chiefly interested in collecting
beetles. This taste, which lasted through all his young manhood, is
the one early indication of the traits that were later to develop. At
first in the day-school and later in the preparatory school Charles
Darwin was anything but a satisfactory student. Even a kindly desire
later to make the most of him makes it impossible to find traces of
any especial fondness for earnest study. He himself believed his
education to have been nearly useless, although he doubtless
under-estimated its value. At the age of sixteen he went to Edinburgh
at his father's desire, to study medicine. The sight of the
dissecting-room nauseated him completely, and he refused to continue
working in it. Later an operation which he witnessed in a clinic at
the hospital sickened him so thoroughly that he declined to attend
further operations. It became evident that the young man was not
adapted to the life of a physician. The next move was to educate him
for the church, and for this purpose, at the age of nineteen, he went
to Cambridge. Here it soon appeared that he was no better adapted to
the ministry than he was to the practice of medicine, and his
university career went on in very desultory fashion. Most of his work
was distinctly neglected, but two of the men he met there were to
influence largely his future life. Henslow, the botanist, was
unusually fond, for a professor in those days, of work in the field.
Charles Darwin's tastes coincided with those of Henslow, with whom he
formed an intimate friendship. He was always welcomed as a companion
on the field trips. Though he studied little of botany in the
classroom or laboratory, he was constantly with Henslow or with
Sedgwick in the field. Sedgwick was the professor of geology, and of
him Darwin was particularly fond, and under him did much the largest
amount of his study. When he came up for graduation he ranked tenth of
those who "did not go in for honors," a not very remarkable class
standing. He was still required to put in two years of residence, and
during this interval he spent most of his time with Sedgwick in the
study of geology in the field. Returning to his home after a
geological trip into Wales, Darwin found awaiting him a letter from
Henslow, offering him an appointment that opened to his ardent mind
the door to a career after his own heart.

The British nation, being the greatest commercial nation of the globe,
has the greatest need for accurate charts of all the seas. Frequently
she has sent out great charting expeditions to various parts of the
world. One of these was to go out in Her Majesty's ship, _Beagle_, for
a voyage around the world. Captain Fitzroy was in command, and he was
especially commissioned to map the coast of South America from La
Plata to Cape Horn and up the western side. In addition to this work,
by carrying a set of accurate chronometers, he was to check up the
longitude of the various ports to be visited in this circumnavigation
of the globe. It was customary on such expeditions to carry a young
man whose duty it was to study the natural history of the countries
visited on the trip. The salary of such a naturalist was so small that
an experienced man could scarcely afford to take the place. Therefore
the appointment usually went to a man rather of promise than of
achievement. Through Henslow's influence, Charles Darwin was offered
this position in 1831. Darwin hastened to obtain his father's
permission, but the elder Darwin at first declined to consider the
matter. He felt that his son had not made such use of his time at the
university as warranted the hope that much could be expected of such a
journey. He believed it necessary that Charles should have some means
of earning an adequate living before he could think of devoting his
time to science. Charles found an efficient advocate in the person of
his uncle, Josiah Wedgwood, Jr. Together they persuaded the father of
the propriety of giving to Charles this opportunity to follow out his
real tastes and ambitions. Accordingly, at the age of twenty-two, we
find him embarked on a journey around the world. In the cabin of the
_Beagle_ he had abundant time, in his long sail across the Atlantic,
to read the two volumes of Lyell's "Elements of Geology," which
Henslow had handed him, with the suggestion that he read it, but on no
account believe it. Filled with the love of geology as Darwin was,
this epoch-making book was exactly the stimulus needed. Lyell had just
begun to persuade the world that to understand the past we must study
the present. In the forces now at work he saw cause enough to account
for all the history of the past of the earth.

There is little doubt that this book was one of the most potent
factors in determining the bent of Darwin's mind. His entire
educational experience had failed to appeal to him. It is fortunate,
we now know, that this was the case. If the university course of the
time had really seized him it would have made but one more student
like hundreds it was turning out each year. For most of us this is the
happy event. Now and then comes the rare spirit to whom all of this
fails to appeal because he is ready for something better. Such was the
spirit of Charles Darwin. He started on his journey with a mind
singularly free from prepossessions. In the long hours of this sailing
voyage across the Atlantic Ocean Darwin had time to read and ponder
Lyell's weighty words. By the time he reached the Brazilian shore he
was filled with Lyell's conception that the present is the child of
the past, developing out of it in orderly sequence. Lyell expressly
denied that this is true of the animal and plant world. He applied it
only to the face of the earth, with its mountains of uplift and its
valleys of erosion. But the underlying principle of an orderly
development under the action of natural causes was there. In Darwin's
mind this at once found acceptance, and was destined to a fruition its
author had expressly disclaimed.

The narrative of this voyage, as subsequently written, describes the
islands visited by the _Beagle_ in crossing the Atlantic Ocean. The
contrast between the simple and general interest in these islands and
the care with which Darwin described the Galapagos and the Keeling
Atoll visited later in the voyage are speaking evidence of the rapid
development going on in the mind of the young naturalist.

Reaching the shore of South America, Darwin first turns to its
geology. But before long the animal life attracts his attention. In
the Brazilian forest Darwin had his first experience of the wealth of
animal and plant life in the tropics, and, like all naturalists, he
was very enthusiastic over it. Among the animals that particularly
attracted his attention was the sloth, a peculiar creature climbing
slowly about the trees, small of size and sluggish of habit. Another
animal that interested him greatly was the little armadillo with its
interesting habit of curling up in its plated skin.

Captain Fitzroy soon finished what work he was required to do in this
neighborhood, and Darwin was called back to the _Beagle_ to continue
his voyage. When they arrived at the mouth of La Plata their most
serious work began. Here there was much tedious charting for Fitzroy,
and Darwin could now leave the vessel for a lengthy trip on shore.
This was doubly welcome. Seasickness was nearly constant with Darwin
while on this entire voyage and every opportunity to work on land was
eagerly seized. This region, too, was rich in objects of interest and
in strange people. While exploring the pampas, beyond Buenos Ayres,
Darwin came across the skeletons of the great mammals some of which
Cuvier had previously described. He studied these bones with much
care, and recognized at once in the megatherium a great similarity in
structure to the sloth he had seen in Brazil. The enormous skeletons
of the glyptodons struck him also as strangely similar to that of the
armadillo. One evening, seated alone in the broad expanse of the
pampas, the idea suddenly swept over him, stimulated, of course, by
his study of Lyell: "Can it be that the little armadillo and the sloth
of to-day are the degenerate descendants of the enormous megatherium
and glyptodon of the past?" But his mind was not yet ready to accept
so bold an idea and he swept it aside.

The people of this wild neighborhood interested Darwin very greatly,
and he describes them with care. In this connection a charming trait
of Darwin's character comes beautifully in evidence. The absolute
purity of his mind, his utter freedom from grossness, shows clearly in
his account of the first really semi-civilized people he had ever
seen.

A little later, while exploring Patagonia, Darwin noticed the
terrace-like formation of that desolate country. A flat near the sea
was succeeded by a rapid rise, then came another flat. Three of these
terraces in succession stretch back toward the Andes. At the base of
the high terraces Darwin found marine shells, largely similar to those
of the ocean beach so many miles to the east. His study of Lyell led
him to suspect at once that this portion of South America had been
raised in successive stages out of the bed of the Pacific. When they
passed around Cape Horn and up the western coast he hunted for
similar beach marks on the sheer western face of the Andes, and found
them without difficulty, confirming his idea of the recent rise of
this end of the Andean chain.

The _Beagle_ continued its voyage up the western coast of South
America until it reached Peru. Once more the abundance of tropical
life is under Darwin's eyes, but now it is the life of an entirely
different section. The dry climate of Peru furnished him with an
environment distinctly unlike that of the moist Brazilian forest. He
collects now with avidity, gathering especially insects and birds.
Then the ship turned its prow westward across the Pacific, only to
stop five hundred miles out at the Galapagos Islands. This little
group he studied intensely, collecting large numbers of insects and
birds. He had not worked over his collection long before he realized
that each island in the group had peculiarities which marked its
animals from those of any other island. Whenever two islands were
close together in the group the differences in their fauna were found
to be comparatively slight. If, however, he examined the animals from
two islands lying at opposite ends of the group, the differences were
always considerably greater. There was, however, a strong general
resemblance among them all and a distant though not so strong
resemblance to the corresponding animals of the Peruvian coast. On
leaving the Galapagos group, Charles Darwin writes in his diary the
suggestive observation that this little group of rocky islands seems
to be one of the greatest centers of creative activity. It was this
interesting resemblance of the animals of these islands to each other
and to those of the Peruvian coast that finally persuaded Darwin that
they were all related and were all descended from those of Peru. For
the rest of his life, with an intensity which increased with each
year, Darwin persisted in a patient search for the possible agencies
by which such change could have been brought about. The problem,
however, was temporarily eclipsed by a pressing geological question
aroused by his visit to the Keeling Atoll. Here his investigation of
coral reef formation absolutely captivated him. In the case of most
coral islands in the Pacific Ocean the reef exists as a circle of
coral enclosing a lagoon of water. In the center of this lagoon stands
commonly a rocky island. It is plain that this is the foundation on
which the coral built. But, in the case of the Atoll, the coral ring
was present and so was the internal lagoon, but there was no rocky
island. The key to the solution came with an interesting discovery.
Darwin began to put down a grappling iron on the outer side of the
reef and to drag up coral. The farther away from the reef he went the
deeper was the water from whose bottom he pulled the coral. What at
first puzzled him was the fact that so long as he dragged up his coral
from depths of a hundred feet or less the coral was alive. Whenever he
went to depths of much more than a hundred feet, his coral was always
dead, though he was evidently pulling it from situations in which it
had grown. Then Darwin remembered the rising Andes, lifting themselves
out of the bed of the Pacific. Here was the correlated movement. The
bottom of the ocean here was sinking. As it sank it dragged down the
corals with it. But the descent was so slow that new corals could
build on top of the others fast enough to keep the reef up to the
surface of the water. At the rate of growth of coral, this would seem
to mean that the bottom could be sinking at a rate of only a few feet
a century. But while the reef could keep up to the surface, the rocky
island must slowly sink. Darwin inferred that there must be a rocky
summit within the lagoon, below the surface of the water. A little
sounding soon discovered this island, and the verification of Darwin's
theory of coral reef formation was at hand. The description of this
Atoll and of his theory of its formation won for Darwin the esteem of
geologists when he later presented it in book form.

The voyage was continued around the Cape of Good Hope. Pursuing the
usual course of sailing vessels, the _Beagle_ touched once more at
Brazil, returning home to England in 1836, after an absence of five
years. Charles Darwin himself believed this trip to have been both his
education and his opportunity. He had started on it a rather careless
and indifferent student. He returned from it the most painstaking and
patient naturalist the world has ever known. His father, who had
hardly consented to his going because he believed him not stable
enough to be intrusted to his own devices for so long a period, was
profoundly moved at the sight of him on his return. Believing in
phrenology, as did many of the physicians of his time, his father
turned to his mother and said, "Look at the shape of his head; it is
quite altered"; which, translated into the language of to-day, would
read, "How wonderfully the young man has developed."

A part of Charles Darwin's duty to the British Government was to write
a narrative of the voyage, and this account of his trip upon the
_Beagle_ is one of the great classics of travel in the English
language. It won the confidence and respect of a wide circle of
readers. In his next book he published his observations made at the
Keeling Atoll and announced his theory of the formation of coral
islands. This was a distinctly scientific investigation, and it won
such immediate favor among geologists as to increase materially the
young man's reputation. No one man is ever widely enough acquainted
with the animal world to classify all the specimens gathered on such
an expedition. In accordance with custom, Darwin began distributing
his collections among specialists. Each of these was to identify and
describe, to name, if necessary, the kind of material he knew best.
Among others, Darwin had a considerable collection of barnacles
gathered from boats and wharves in all parts of the world. As he could
find no one sufficiently acquainted with these creatures to classify
them he decided reluctantly to work them up himself. For about eight
years much of his spare time was given to this painfully exacting
work. He expresses himself as fearing it was a waste of time. Few
systematic workers will agree with him. He did his work so well that
it has been unnecessary for anyone to do it again. In addition it
gained him the esteem of a new circle of scientists and that a
decidedly exclusive circle.

The publication of these books did much for Darwin. His narrative of
the voyage gained the good will of cultured England in general. The
book on coral reefs won the geologists. His "Manual of the
Cirrhipedia" (as the barnacle book was called) secured the attention
of systematic zoölogists. The time was not far distant when he would
need every aid possible toward gaining and keeping the regard of men;
for he was to promulgate a theory that would arouse the bitterest
opposition and the keenest scorn.

All the while Darwin was working on these books his mind was quietly
busying itself with what he called the species question. The more he
studied the material collected on his long tour, the more confident he
became that the animals of the present are the altered descendants of
the animals of the past. He tried patiently to work out every
conceivable hypothesis to see whether he could account for the
alteration. He felt quite sure animals changed, but how they changed,
and why, he could not for a long time conceive. He knew that gardeners
were constantly producing new varieties of plants, and that animals of
various breeds were clearly the descendants of other and familiar
varieties. Accordingly he began to study the methods of animal and
plant breeders, to visit their farms, to open correspondence with them
and read all their trade journals, to undertake experiments in the
breeding of plants. The longer he worked the more confident he became
of the reality of the change; but for a long time no glimmer of the
cause by which it could be brought about came to his mind. In 1838 he
came across a book by Malthus called "An Essay on Population," in
which the author shows that, whereas man increases by a geometric
ratio, he cannot hope to increase his food supply in more than an
arithmetic ratio. That is, while the food might increase like the
series 2-4-6-8-10, the population would increase like the series
2-4-8-16-32. On this basis it is only a question of time when the
earth will be too full of people for it to be possible for the food to
sustain them. Malthus added many observations and suggestions, but
this is as much of the book as interests us in this connection. Here
was the idea that suggested to Darwin his agency for producing the
change of the animals of the past into those of the present.

The number of animals of any particular species remains practically
the same. There may be a few more one year, and a few less another,
but on the average, year by year, the number of toads, the number of
blacksnakes, the number of field mice, remains sensibly the same.
Sometimes the rise of man brings an end to the wild population, and so
in the past animals have dropped out of the race. Yet in the long run
and for a considerable time the number of any species is constant. But
each animal produces offspring in quantities sufficient to far more
than replace himself as he dies out. In other words, animals increase
not by addition but by multiplication. Too many are born for all of
them to live. What becomes of the great mass of them? The answer is
they die; most of them die young. Only a few fortunate individuals,
favored by being a little stronger, a little more cunning, a little
more attractively colored than their mates, survive to carry on the
race.

The skillful gardener, looking over his flowers, finds a plant of more
than ordinary beauty and thrift of growth. When it comes to maturity
he keeps its seeds separate from those of the rest and next year
plants them by themselves. As they come up he weeds out all unthrifty
plants, only allowing the strongest to come to maturity. As they break
into bloom he plucks away all whose flowers do not come up to the high
standard he has set for himself. After a while he has but a few plants
left, but these are the thriftiest and bear the most beautiful
flowers. Again he allows these to mature and selects the seed of the
very finest. Next year the process is repeated. After a few
generations, usually three if the man is skillful enough, he has a
definite strain of flowers that will thereafter come true. This is the
process of artificial selection as carried on by man.

Darwin saw that Nature is constantly carrying on a similar process.
She produces seeds enough on almost any plant to clothe the world in a
few years if all of them could fall into proper ground and thrive like
their parents. A friend of mine found a mullein stalk that bore more
than seven hundred seed pods and averaged more than nine hundred seeds
to the pod, a total of more than six hundred and thirty thousand
seeds. If each of these could find lodgment on a plot eighteen inches
square, produce a similar number of seeds and plant them all, the
result would be overwhelming. The fourth generation would cover land
and sea, from pole to pole, one hundred layers deep. But there is no
such danger. Year by year the mulleins hold their own and no more. Any
particular field may have more or less, but in the long run the
average for a district is about the same. Some of the seeds are poor
and thin. These scarcely sprout. Others spring up into thin-skinned
plants, and the first frost nips them. Still others lack the woolly
coating in its finest abundance, and the browsing animals eat these.
Others lack power to put out a wide-ranging root supply and the first
drought kills these. Still others fail to send up a vigorous stem and
the passing animal knocks them over and they die. Of the few that are
still surviving, some produce such small and inconspicuous blossoms
that the insects scarcely see them, and they go unfertilized. In the
end only the aristocrats of the group are left, aristocrats in the
best sense of the word. These are strong, thrifty, and beautiful, and
are provided with every defense known to the mullein world. From these
the mulleins of the next generation will spring. Again Nature will
select the best of these, by a repetition of the same process. Thus
year by year the stock is improved. Any new feature that is favorable
helps its possessor to survive, and, if happily mated, will show
itself after a while in the entire group. This, in brief, is the
underlying idea of Natural Selection, as Darwin conceived it.

In 1842, at Lyell's suggestion, Darwin wrote a short sketch of his
ideas which he, two years later, expanded into a somewhat larger
account. The manuscript of these early views of the theory was
completely lost and has only been recovered within the last few years.
It was recently published under the editorship of Charles Darwin's
son, Francis. It is astonishing to see how clearly the first short
sketch states the underlying conception which all of Darwin's
subsequent work amplifies. Hooker was constantly urging Darwin to
write out his whole theory in the form of a book, and Darwin had begun
to do so in 1856.

Meanwhile, down in the Moluccas, Alfred Russell Wallace had been lying
sick of a fever contracted during his exploring expedition in that
neighborhood. He had been studying the distribution of the animal life
of the Malay Archipelago. Overcome by sickness, as he lay in bed, he
began to think over a book which he had read not long before, "Malthus
on Population." Wallace had been pondering on the question of the
origin of the animals of the Malay Archipelago. He had not the
faintest knowledge of what Darwin was doing, but was influenced, of
course, like Darwin, by what he read in Malthus. Interesting to
relate, he had come to exactly the same conclusions, writing his
opinions in the form of an essay. By the strangest sort of
coincidence, he sent this essay to Charles Darwin, asking him to read
it, and, if he thought it was not altogether too foolish, to send it
to Lyell for publication by the Linnæan Society. Darwin read with
utter astonishment this essay containing views so absolutely like
those that had come to him from his own long series of observations
and reflections. With uncommon magnanimity his first impulse was to
withhold his own publication entirely, but to this Lyell and Hooker
would not for a moment consent. They were determined that Darwin
should give them his long series of notebooks as evidence of the
independence of his work and that he present to the Linnæan Society,
simultaneously with Wallace's paper, one of his own upon the same
subject. In this manly form both essays were read at the next meeting
of the society. The joint papers provoked instant discussion and
prompt opposition. The world at large scarcely admitted a possible
doubt of the fixity of species. Men generally believed the idea to be
absolutely irreconcilable with their religious faith. Any question of
the fact that the species of to-day exist practically as they had been
handed down to the earth in the beginning by the Creator himself
seemed to most men a direct blow at religion. At this time a very
large number of natural scientists were clergymen, hence the
opposition had abundant and influential support. The storm grew
fiercer and more widespread. The publication in 1859 of Darwin's great
book on "The Origin of Species by Means of Natural Selection or the
Preservation of Favored Races in the Struggle for Life" added fuel to
the flame.

In 1860 the British Association met in Oxford, and Bishop Wilberforce,
the retiring president, in accordance with the custom of the society,
gave a summary of the advance of science, especially during the
preceding year. Everyone knew perfectly that the bishop would deal
with the species question, and that he would handle it severely.
Darwin was prevented by his usual ill health from being present at
this meeting, but Huxley was there to see that their side of the
question received proper attention. The bishop made a lengthy address,
in the major portion of which he brought forward entirely worthy
objections to Darwin's theories. Toward its close his feelings
overmastered him and he departed from his manuscript and unburdened
his mind. The lack of stenographers in those days and the tenseness
of the moment, which made everyone forget to take down what was said,
make it impossible to tell exactly what happened. It seems that Bishop
Wilberforce, appealing to the prejudices of his audience, said, in
language that now seems ludicrous but then was terribly bitter:
"However, any of us might be willing to consider ourselves descended
from an ape upon his father's side, no one would so demean his
mother's memory as to imagine that she could possibly have shared in
this descent." Huxley, who had waited patiently for the close of the
bishop's address, saw immediately the fatal mistake. Turning to his
companion beside him, he said, "The Lord has delivered the Philistine
into my hands," and, rising, he hurled back at the bishop the
indignant reply, "I should far rather owe my origin to an ape than I
would owe it to a man who would use great gifts to obscure the truth."
The bishop had made the mistake, and the struggle was on. Year by year
it raged. One by one the scientists, first of England, and then of
Germany, took their stand by Darwin. Huxley in England and Haeckel in
Germany were the foremost advocates of the Darwinian idea. Long and
fiercely the battle raged; slowly and gradually men began to see that,
instead of undermining religion, the idea of evolution uplifted
creation and made it not a strange happening in the distant past, but
a divine activity through all time. But the battle had by no means
subsided when one day came the sad news that Darwin's heart, so long
feeble, so serious a hindrance to his work, had beaten its last on
April 19, 1882.

His own people wished to bury Darwin quietly at his home in Down, but
Darwin now belonged to the nation. A petition signed by many public
men was sent to the Dean of Westminster, asking that his body might be
granted burial in the Abbey. Probably no greater honor can come to man
to-day, and fortunately Dean Bradbury was broad-minded enough to
acquiesce. So it came to pass that the church that had so long
believed him her enemy, that had first so bitterly fought him, came at
length to see that he added a new dignity and worth to her faith, and
took him to her bosom. Darwin's body lies buried in the Abbey.

In all the glorious company of immortal dead whose earthly frames are
gathered in England's great mausoleum, there is no other one who has
done so much to modify the mind of thinking man.



CHAPTER III

THE UNDERLYING IDEA


We have seen in the preceding chapters how the idea of evolution
worked its way through the minds of men. Man after man got a glimpse
of the idea, even among the ancient philosophers. But no one could
speak convincingly on the subject before modern times, when a wider
acquaintance with the animal world gave a body of facts on which it
was safe to base conclusions. Even then the idea eluded men, until
there came a worker trained by a long voyage around the world in which
he had nothing to do except to study nature. He finally gathered in
his mind material sufficient to convince himself not only of the truth
of evolution but of the process by which this evolution was brought
about. Every scientific principle is simple in its basal idea. In
actual life the action of the principle may be so bound up with others
as to need a skillful mind for its detection. But under all the
complexities and modifications, like a silver thread woven into a
cloth, runs the basal idea. Until a master has detected it the
presence of it may be unsuspected. But once discovered and expounded,
thereafter anyone may follow out its workings. So it is with the
Darwinian idea of selection. It waited long for a discoverer, but,
once found, we cannot but wonder why men did not see it earlier, it is
so simple.

Mr. Darwin's mind, while slow and cautious, had a wonderful
perseverance. When he had finished his work he had not only given a
clear account of the process of evolution, but he had foreseen almost
all the valid objections that were afterward to be brought against his
theory. Some of them he had explained quite fully; of others he
indicated a possible explanation; of still other questions he
confessed that as yet they were not plain. But the whole theory is so
simple in its fundamental ideas that it has completely revolutionized
the whole aspect of modern biology and, indeed, of modern thinking in
many lines.

There are four underlying conceptions, each simple in itself, which
must be clearly perceived before one can understand Mr. Darwin's
theory of "Natural Selection." The first of these is known under the
name of Heredity. It is a matter of common observation that every
animal or plant produces offspring after its own kind. Under no
conditions would we expect a duck to lay an egg from which could hatch
anything but a duck. No Plymouth Rock chicken mated with another of
her own kind will ever lay an egg that will produce a Rhode Island
Red. We may believe that the dog has descended from some form of wolf,
but it is not meant that at any particular time in the past any wolf
mated with a wolf ever produced pups that were anything but wolves.

Why this should be so is one of the most profound problems of biology.
Nothing but the fact that the process has gone on under our eyes for
so long a time could blind us to its marvelous character. To open the
egg of a chicken and examine it by the most refined methods known to
science is to find in it absolutely nothing that could be by the
widest stretch of the imagination considered anything like a chicken.
The biologist who has examined such eggs before and knows them in all
stages of the process may recognize in an egg which had been incubated
for a short time something which his previous experience tells him
will become a chicken. But it has not the faintest resemblance to a
chicken until later in its development. In early spring one may gather
pond snails from any country stream and place them in an aquarium. The
change from the cold water on the outside to the warmer water of the
aquarium and the temperate climate of the room hastens the process
which in the stream would not take place until later. In a short time
one may find fastened to the glass side of the aquarium the little
mass of transparent jelly which surrounds and protects the delicate
eggs of these creatures. Fastened as they are it is easy to direct a
magnifying glass so as to observe the change which goes on within
these transparent eggs. It is even possible to apply a microscope in
such a way as to watch the transformation under the low power of the
glass. At first the eggs are as clear as water, having at the center a
slightly yellowish spot. This central mass divides and subdivides
until the separated sections grow so small and numerous as to lose
individuality. Then the mass begins to press out here and dent in
there. After a little while a double line of fine, hairlike
projections runs around the creature. These hairs wave in such fashion
as to make the embryo snail revolve slowly in its egg. A little later
and swellings become more pronounced over the surface. One side
flattens; the rotary motion stops; eyes appear at the front of the
animal; a hump on the back begins to be covered with a shell, and the
little creatures, pushing from the jelly, start their life journey on
the side of the aquarium. Why did it happen? How did it happen? Here
we have seen creation at work. Here surely the hand of the Creator is
working in the only sense in which the Creator may be properly said to
have a hand. How the history of the substance out of which the egg was
produced provides for the future development of that egg no man has
yet clearly said. This is not to say that we shall never know, still
less is it to say that this can never be known. Ralph Waldo Emerson
has said that there is no question propounded by the order of nature
which the order of nature will not at some time solve. If he is right,
and I believe he is, we shall at some time know how it is that this
egg produces this snail. But, as I said before, nothing but the
frequency with which the process goes on under our eyes could possibly
blind us to the marvel of it.

The regularity with which each animal reproduces its kind is no more
surprising than the faithfulness of that reproduction. Some of our
birds have wonderful markings on their plumage. It is astonishing to
see with what fidelity the feather of a bird may reproduce the
corresponding feather of its parent. It will occur to everyone how, in
the human family to which he belongs, there is some little peculiarity
which, while not appearing in every member of the family, when it does
appear is remarkably uniform. It may be only the droop of an eyelid,
it may be a tendency to lift one side of the lip more than the other,
it may be the peculiar shape of a certain tooth in the set, and yet
when it appears it comes with astonishing similarity in all who
possess it. So much for the principle of Heredity.

The second great underlying idea is known by the name of Variation. We
have just been dwelling on the regularity with which parents produce
offspring like themselves. We must now draw attention to the fact
that, while it is true animals must absolutely belong to the same
genus or species, even to the same variety, none the less no animal is
exactly like his parents. Furthermore, in a group of animals produced
at the same time from the same parent each one will have at least some
small point in which he differs from every other one in the group. Two
animals may look alike at first to the undiscerning eye, but a keen
analysis of the measurements of the various parts of their bodies will
show distinct differences. This is quite as true among lower animals.
A toad may lay a double string of four hundred eggs which may be
fertilized by the same male at the same time. These eggs may develop
into tadpoles in the same pool not over a foot square. Within a few
weeks these little toads may have gained their legs, lost their tails,
and all may have left the water and taken to the ground upon the same
day. Already the careful observer will notice differences among them.
Some are larger than others, having grown more rapidly even though
their surroundings were exactly the same; others are more skillful in
their peculiar method of throwing the tongue at an insect they wish to
catch. Still others will be differently colored. They might be
arranged to show a considerable gradation between the lightest and the
darkest of the group, though there may not be anywhere in the row a
considerable gap. It is variation in animals of the same parentage and
same surroundings which in the mind of Mr. Darwin made evolution
possible. He always favored the idea that it was the continuous
accumulation of these small variations that finally produced the
profound changes which mark the new species. He admitted the
possibility of the occasional appearance of those more distinct leaps
in variation on which the present school of mutationists so strongly
insists; but he believed them to be less influential, in the general
trend of evolution, than the slower but much more frequent variations.

One of the most complicated and perplexing problems in the biology of
to-day is the question of the origin of these variations. It is quite
as hard to understand as is the method by which animals produce their
own kind. No problem is being more earnestly studied. Suppositions we
have in considerable number, and two of these at least may reasonably
be mentioned. We will consider first the less certain theory. There is
nothing in the egg that in the remotest degree resembles its parent.
The old idea that every acorn had in it a miniature oak which only
needed to unfold itself, or that the hen's egg had within it a
miniature chick which only needed the warming process in order to make
it evident, could not possibly survive the invention of the
microscope. We may not, and we certainly do not, know everything that
is in one of these eggs, but we do know most certainly that what is
there has no resemblance to what it will be in time. The biologist
finds in the nucleus or central core of every growing and reproducing
cell certain minute bodies which Weissmann believes do much to
determine the growth of the rest of the cell. He believes also that
there are many more such "determinants" than are necessary for the
reproduction of the cell. Each of these determinants may be fitted to
produce slightly different results, but what decides which of them
shall have its own way is quite uncertain. It may be that one
determinant happens to be more favorably placed than others in the
cell and that it has consequently secured more of the nourishment that
comes to the cell in the blood of its parent. If this is true it would
certainly be favored in the competition. We are becoming quite certain
that whatever variations arise really start in the egg. The simplest
conception as to the cause of variation would seem to be varied
experience. One man trains his brain, another his hand; and in each
case the organ so trained develops. But science is strongly of the
mind that such influence does not reach the next generation.

A musician may have taught his fingers to be nimble; may have given
them speed of motion and precision in their action. No child of his
born after he acquired this wonderful facility of execution is any
more likely to be a skilled musician than a child born before he had
ever practiced enough to be anything more than a crude performer.
Science is nearly certain that his children are just as likely to be
talented along musical lines if he himself never had become a
musician, simply because he had it in him to be a musician. In other
words, they may inherit the talent which he developed, but they
inherited it not because he developed it, but because it was in him to
be developed. This is in accordance with the famous principle that
there is no inheritance of acquired characters. We shall touch this
question a little more fully in a later chapter, in speaking of the
development of the evolution theory since Darwin's time.

If we are right in this matter, and we certainly are nearly right,
variation must take place for the most part in the germ. These
variations may not show until the animal has grown up, but they must
have taken place among the determinants in the germ cell or they would
not reappear in subsequent generations.

There is another process by which new variations may arise and which
is more easily understood. It is the method of double parentage. The
Barred Plymouth Rock chicken had its origin in such a double ancestry.
The one parent was a Black Java whose color has disappeared entirely
in the cross, but whose single comb with its few large points comes
out clearly in the newly produced fowl. The other parent was a Barred
Dominique. It is to this parent that the Plymouth Rock owes the
interesting cross markings on its feathers. The comb on the head of
the Barred Dominique is of the type known as the rose-comb, having
many rows of slight projections. This has completely disappeared from
the Plymouth Rock fowls. I am told that the skilled chicken fancier
can tell, concerning many points in this fowl, to which of the crossed
ancestors each quality is due. To a certain extent it is undoubtedly
true that here we have the secret of the origin of many of those
interesting people whom we are pleased to call geniuses. They may not
possess any qualities not clearly discernible in various of their near
ancestors, but in them we find what we, for the lack of a better
understanding, call chance combination in one individual of the finer
qualities of many ancestors, and this individual is so placed in life
as to have these qualities developed and strengthened.

Charles Darwin, humanly speaking, may be accounted for as the happy
combination of a double heredity and a favorable environment. He
inherited the scientific inclinations of his grandfather, Erasmus
Darwin, and the patient, sturdy honesty of his other grandfather,
Josiah Wedgwood. These developed under the stimulus of the long
five-year voyage, face to face with the world of nature. This happy
complex produced the master biologist. To believe that he came about
purely by chance requires a great stretch of the imagination. "There's
a divinity that shapes our ends."

We have endeavored to make clear two of the basal ideas underlying
evolution. One of these is responsible for the continued production of
animals or plants of the same kind, preventing the world from becoming
a wild kaleidoscopic and fantastic dream. Heredity is the conservative
force of nature. The other idea underlies the development of new
departures which keep the world from being a dull, dead, unending
repetition of the same monotonous material. Variation is the
progressive tendency in nature.

The third basal idea is that of Multiplication. Animals and plants
multiply; they do not simply increase, they increase in a geometrical
ratio. Anyone who has worked out one of these geometrical ratios knows
how wondrously they mount up. There is an old familiar story of the
blacksmith who asked the price at which the stranger would sell the
horse he was shoeing. The owner of the horse replied that, if the
blacksmith would give him one penny for the first nail he drove into
the shoe, two for the second, four for the third, and so on, he might
have the horse. No hundred horses in the world taken together have
ever brought such a price as the blacksmith would have had to pay for
the animal on which he was working. This is no circumstance to the
awful story of what would happen to the earth if any animal could
multiply unrestricted. The usual number of eggs laid by a mother robin
for a single brood is four, and she may produce two broods in one
season. This would mean that the original pair had produced eight
offspring, four times their own number. If we can imagine these mating
the next year and producing their kind in the same proportion; and, if
we further suppose that each robin needs a space one hundred feet
square from which to gather his food, we realize the astonishing fact
that in fifteen years every patch one hundred feet square in
Pennsylvania and New York would each have its resident robin, while
the following season would find a robin on every similar patch from
Maine to the Carolinas. Of course this could never happen, this is
simply what would happen if all the robins could grow to maturity and
reproduce at the normal ratio. But the robin is a comparatively slow
producer.

Our turtles are more prolific. Twenty eggs would probably not be an
unusual number. If we could imagine a turtle to live in the sea and to
produce at this rate; and, if each turtle should need as much room
each way as the robin, and a depth of water equal to its width, before
the robins had spread over New York and Pennsylvania the turtles would
have filled all the seas of the globe. Frogs are even more remarkable
in this respect. Two hundred eggs is not an uncommon number. If each
frog required a space twenty-five feet square on which to subsist, the
entire earth would be more than covered with them within six years. It
is ludicrous to think of such numbers, especially when we realize the
hundreds of thousands of kinds of animals there are in the world, each
of which is also multiplying, and it becomes evident at once that only
an infinitely small proportion of all these creatures can possibly
survive. This, then, is multiplication.

Here comes into play the fourth basal idea in Mr. Darwin's
explanation. This is the part of Selection. When man produces new
varieties of animals he does it by picking out from his flocks or his
herds such as conform most nearly to his idea of what is desirable.
These he mates, and from their progeny he selects the ones that suit
him best. Generation by generation he gets his domesticated animals to
conform more nearly to the standard of his desires. Natural selection
works in exactly similar fashion. Of all the eggs that are produced by
the animals at large in nature an overwhelming proportion never
develop at all. They dry up, are eaten by their enemies, find no
suitable place or time for development and decay, or are overtaken by
some other calamity. Of the animals which emerge from the remainder an
overwhelming majority come to an untimely end within the first few
days of life. Each has countless enemies which prey upon him, and
these have scarcely devoured him before they themselves become the
prey of some stronger creature. Until Mr. Darwin gave us his elemental
idea it was taken for granted that it was a matter of pure accident
which survived and which yielded in the struggle and cares of life. It
was Darwin who showed us that in this tremendous struggle against
those of his own kind in the search for the same food, against the
elements, in securing a mate, any animals possessing a superiority,
however slight, must have some little advantage in the battle.
Certainly, where so many must utterly fail, only those could possibly
succeed who were well fitted to the circumstances in which they must
live. We used to think animals were destroyed by the "accidents" of
life and no one could foretell accidents. Mr. Darwin made clear that
it was not a question of chance. That which might happen to any
individual animal might be what we, not knowing the process, called
accident, and yet there could be no possible doubt that those who
succeeded were better fitted to battle with life than those who
failed, and that their success was due primarily to their being thus
advantaged. Consequently, if generation by generation the so-called
accidents of life are constantly eliminating the unfit in overwhelming
proportions, not only must the positively unfit disappear, but even
the less fit. The more keen the struggle, the fewer could survive and
the fitter they must be to survive at all. This is Selection. These,
then, are Darwin's four great factors of evolution: Heredity,
Variation, Multiplication, Selection.

From these it results that the animals and plants naturally become
better adapted to the situation in which they are placed. When, as is
constantly happening through the history of the earth, a change occurs
in the physical geography of any region, when a plain is lifted to be
a plateau, or a mountain chain is submerged until it becomes a row of
small islands, this alteration will produce uncommon hardships among
animals, even though they were well fitted to the old conditions. Any
animal or any species of animals which meets such a calamity has
before it only three possible outcomes of the struggle. First it may
be plastic enough and it may vary enough in the right direction to
adjust itself to the changed conditions. In this case it and a favored
few like it will occupy the altered territory. The second possibility
is that it may migrate while the actual change is going on, thus
remaining in the sort of situation suited to it and its kind. The
third possibility is the one which overtakes a great majority of
animals--they die. Even the entire line dies out, and the strata of
the rocks are filled with the bones, shells, and teeth of such as have
met this fate. They have become extinct.

Thus far in this chapter we have been considering the influences under
which it is conceivable that animals should advance. There is no
question whatever that there are too many animals born, nor is there
any possible question that a very large proportion of them must
certainly die. There is equally no doubt that every animal produces
after its own kind, and that its offspring, while they resemble it
closely, still vary a little from it and from each other. This fact is
perfectly plain to the most superficial observer who thinks on the
matter at all. It is not so plain, nor is it easily demonstrated, that
all of these acting together do surely, even if slowly, alter the form
and behavior of the animal world. It is difficult to prove that there
is going on under our eyes a steady and real improvement in the
adaptation of the animals and plants around us to the situation in
which they are placed. As far back as man's memory runs they seem to
have been about what they now are; as far even as man's historical
record runs they seem to have suffered no great alteration. The
Egyptian of the old tombs is much like the Egyptian of the same rank
to-day. The African of the tombs has the African features of to-day.
Under such circumstances it is hard to prove that there is a steady
and undoubted advance. For the most part the balance of the animal
world is fairly even, and any species does not ordinarily change
rapidly enough or migrate widely enough to show us its new features.
It is difficult to see the struggle which we are so sure is going on.
The life of animals is so hidden in many of its details that their
joys and sorrows, if such we may call them, scarcely fall under our
observation. Now and then an opportunity comes to see the process of
adaptation work itself out. The struggle for existence begins anew and
is carried on with special vigor, with victory, temporary or
permanent, to one of the participants in the struggle.

The opportunity to observe such a change is presented in the United
States by the introduction of the so-called English sparrow. This
little creature, received at first with such joy, soon became the
object of an almost bitter hatred on the part of very many people.
This is really due to the fact that this bird is one of nature's
darlings and thoroughly succeeds where it has an even chance.

The number of birds of any particular species which a region will
support seems to be fairly definite. If a species is especially
protected until it becomes unusually abundant, the removal of the
protection commonly brings it down promptly to its original numbers.
On the other hand, an accident of severe character or a special
persecution may much diminish the number of the species, and still it
will, within a comparatively few years, return to its previous
abundance.

The inhabitants of Florida who own orange groves will never forget the
winter of '94-5. A bitter cold wave swept along the coast and killed
such large numbers of orange trees as almost to cut Florida out of the
orange market and to open the gate to California, who was eagerly
offering her fruit. This same frost caught the migrating blue birds
and killed them by the thousands. When spring came bird-lovers
throughout the eastern United States found an astonishing scarcity of
these favorites. It was feared that with numbers so small they could
not possibly compete with their enemies and with whatever untoward
circumstances should be their lot. But there is room in this
environment for a definite number of bluebirds. When this number was
suddenly reduced the chances to make a bluebird's living were so
wondrously multiplied that young bluebirds had such an opportunity in
life as their fellows had not had for many long years. Accordingly
they thrived as never before, and, of their progeny, a larger
proportion lived to the following year. It was only a few years before
the number of bluebirds had risen. Now we probably have as many as we
have had for a long time past. I cite this simply to show that a
region can support a certain number of animals of any one particular
kind, and that the animal is likely to multiply, if given a fair
chance, until it has reached such proportions. Now to my story of the
rapid development of a newcomer.

In the year 1850 a resident of Brooklyn came home from a trip to
Europe. He was a lover of birds, and while in Europe had been
particularly attracted, no one now knows quite why, to the common
House Sparrow, as it should be called. It is no more abundant in
England than in many parts of the continent of Europe. A name that has
been used for a long time is very hard to cast aside, and we shall
probably continue to mistakenly call him the English Sparrow to the
end. Our Brooklyn traveler brought home with him from Europe eight of
these interesting little birds and succeeded in inducing his
colleagues in a scientific society to share his interest in them. Not
wishing to commit the newcomers suddenly to the rigors of the American
winter, these men built a large cage for the sparrows, meaning to set
them free in the spring. For some reason or other when the winter was
over the birds were all dead, and this first attempt to introduce the
sparrow into America failed entirely. The little bird had won so many
friends that his success was now sure. Finding a favorable
opportunity, these Brooklyn men dispatched an order to a man in
Europe, asking him to supply them with one hundred English sparrows.
The consignment came in good shape and the birds were liberated on the
edge of Brooklyn. This was the first of a number of introductions. A
little later New York City sent for two hundred and twenty of these
interesting creatures and turned them loose in her parks, while
Rochester, with what was then considered great public spirit,
purchased one hundred for herself. But the most progressive city in
this respect was Philadelphia. She had long been troubled with the
spanworm on her trees. This detestable larva had the unpleasant
fashion of lowering itself by a long silken thread from the shade
trees then so abundant in that beautiful city. The spanworms traveling
around over the clothing of the passersby were so objectionable to
everybody that it was with greatest delight that Philadelphia heard
of the new birds which ate the pest. One wonders why some
ornithologist did not look at the bird long enough to see that it had
the sort of a bill characteristic of birds that eat seeds. It is true
that most birds feed their young on insects, hence there is a time
when any bird is apt to be insectivorous. But the structure of the
sparrow's bill, like that of all finches, should have warned these
bird-lovers that the sparrow was not to be depended upon to earn his
living by catching worms. It is easy, however, to be wise after the
event. Philadelphia believed she was engaging in a particularly
advanced movement when she imported from England one thousand English
sparrows, nearly as many as were liberated by all other cities
together. These birds were turned loose among the shady streets and
wide spreading parks of the City of Brotherly Love.

It is a serious matter lightly to disturb the balance of nature by the
introduction of a new species. It is true that the sparrow did eat
some spanworms and for a while enthusiastic bird-lovers hoped that
here was the solution of the difficulty. Philadelphians will also
remember that, with the spanworm removed from competition, the tussock
moth, whose caterpillar carries on his back a series of yellow, red,
and black paint brushes, at once become the permanent parasite of the
long-suffering shade trees. This caterpillar is covered with bristling
hairs, very closely set. Almost any bird objects to hair in his
victuals; and this particular larva has hair more than ordinarily
objectionable, for it irritates wherever it pricks the sensitive skin.
This coating seems to protect the caterpillar from the sparrow, with
the result that Philadelphia's trees were soon nearly defoliated by
this comparatively new pest, worse than the spanworm. With the paving
of the city's highways and the consequent shutting off of the air from
the roots, the trees have largely disappeared from the streets of
Philadelphia. With them have gone a fair portion of the tussock worms,
but the sparrow holds his own. Here is a new bird in the field, and
the struggle for existence on the part of every other kind of bird is
now more complicated and severe. The sparrow can live where the rest
of the birds have no possible chance. He throve so well in this
country that by 1875 he had spread over five hundred square miles in
the neighborhood of our larger Eastern cities. Thus far almost
everybody was pleased with the new introduction. Within the next five
years he had spread over more than fifteen thousand square miles, and
wise men were beginning to feel doubtful of the virtues of their
aforetime friend. When by 1885 more than five hundred thousand square
miles had been occupied by the enterprising little fellow, there
remained no longer a doubt in the minds of most people that the
sparrow was an unmitigated nuisance and great fears were entertained
that he had multiplied to such an extent as to be a serious menace.
Here, then, is a modern instance under our own eyes of a victory in
the struggle. If the sparrow has multiplied rapidly, while all the
other birds have either only held their own or even have diminished in
numbers, it is quite evident he must be better fitted to the
conditions than they are. What are his fit points? Why does he succeed
while others fail? The thoughtful bird-lover will have little trouble
in understanding at least some of his victory-winning characteristics.
How did he come to be almost the only bird who can live in large
numbers in our great cities, without losing his ability to get along
in less crowded situations?

In the first place this interesting bird is a clannish fellow. He has
lost the ordinary sparrow habit and has come to like to live in
crowded groups. Seclusion is not at all to his taste, and if there are
only a few sparrows in the neighborhood those few will most certainly
be found living near each other. One of the early adaptations of the
sparrow to his city surroundings was the ability to find for himself a
considerable proportion of his food in the undigested seed that could
be picked up from the droppings of the horses. This naturally led the
surplus sparrows out through the many thoroughfares leading from any
large city. Where horses went sparrows could follow. Accordingly along
the great lines of travel this bird found the simple path by which he
could enter new territory. Meanwhile box-cars came into our large
cities with freight. Sometimes they had carried grain, sometimes
cattle. In either case it was not unlikely that a certain amount of
grain should be found scattered over the floor of such cars. The
sparrow visited these cars for the grain, and it must have been no
infrequent accident that a door should be shut upon a group of
sparrows, especially in inclement weather, when they were apt to be
huddled in a dark corner of the car. These prisoners would be carried
to the destination of the car and there liberated, thus producing a
new center of what we are now inclined to call infestation. By such
means the English sparrow has spread over much the larger portion of
the American continent. Few birds are bold enough to visit a railroad
car. Of the few who might be tempted, most are timid enough to fly on
the first approach of man. Hence they fail to gain this chance of
spreading. They must remain in the old crowded home. Meanwhile the
sparrow, thus transported, finds a new home with fewer or no sparrows.
The struggle is less keen. More of his kind can live. His boldness
has been here a fit quality and has helped him in the race.

Man is only slowly coming to be a city-dwelling animal. Although it is
a voluntary process with him, he still usually visits the country with
much enjoyment. He has not as yet learned to adapt himself thoroughly
to the city, for somehow city life kills him. Families that move into
the city gradually have a smaller number of children in each
generation until shortly the family is wiped out. The population of
the city must constantly be replenished from the country. But the
English sparrow is more adaptable than are the people. He has made
himself at home in the heart of the biggest city. The Wall Street
canyon is not deep enough, nor contracted enough, nor free enough of
food to blot out the life of the English sparrow. At the heart of the
deepest gully among the skyscrapers of our biggest cities we find this
little bird hopping between the horses' feet, darting out from under
the wheel of the push-cart, fluttering only a few yards to a place of
safety, to return at once to his scanty meal upon the pavement as soon
as opportunity offers. He is a typical city dweller and has learned to
thrive there. Again in this matter he has distanced other birds to
whom the city is more deadly than it is to people.

Another very important element in his fitness for the struggle of
life lies in the fact that he is unafraid of man. He is wary of man;
by which I mean he will quickly fly up from in front of man's feet. It
is exceedingly difficult to catch a sparrow in one's hand. It is far
easier to lure a pigeon within reach. But the sparrow, when escaping
your hands, comes to rest but a slight distance away, only to elude
you quite as successfully if you try again. If the sparrow is let
severely alone he becomes more and more familiar with men, flies less
promptly, and goes a shorter distance, but any attempt to trap him
renders him shy more quickly than almost any other bird we have. He
soon learns to avoid a trap in which his companions have come to
grief. Those who would poison or trap sparrows must change constantly
the base of their operations. This fearlessness of man is a valuable
asset to the bird, for it is an important defense against other foes.

The most serious enemy the birds at large have, after man himself, is
the bird of prey. Hawks and owls capture a large quantity of our
smaller birds. Now the hawks and owls are for the most part shy of
man. They have gotten a bad reputation, especially if they are of any
size, because of their more or less pronounced proclivities for
seizing our domestic poultry, and consequently many people will fire
upon a hawk or an owl who would probably fire upon no other bird. By
living close to man the sparrow is largely saved from the danger of
capture by these carnivorous creatures, and this is the first and a
very important element of the advantage to the sparrow of living near
man. But there is the additional advantage that man scatters about
him, in one way or another, a very considerable amount of waste food.
I have suggested that the seeds in the droppings of the horse form a
large proportion of the sparrow's food, and horses are to be found
only with men. In the neighborhood of man's home, unless he has become
sanitary to a degree which has only been attained in recent years,
there is usually more or less garbage, kitchen offal of one sort or
another. To this the sparrow has easy access and from it he makes many
a meal. But this fearlessness of man gives him still another advantage
which his competitors fear to use, it provides him with nesting sites.

Man has the faculty of putting up ornamental trimmings on his house,
and there is no spot the sparrow chooses more willingly in which to
build his nest than the ornamental quirks and cornices of man's
architecture. A Corinthian column with comely leaves in its capital
seems especially designed for the comfort of the sparrow, and his
distinctly untidy nest is the familiar disfigurement of almost every
ornate public building. These are the advantages which come to the
sparrow from his willingness to associate with man, and there are
comparatively few birds with whom he must share them. Few birds select
the immediate neighborhood of man's home for their nests. They may
live in the neighboring trees, they may haunt his orchard, but his
house, for the most part, they decline to frequent.

Still another quality which makes for success in this buccaneer is the
willingness with which he will vary his food as occasion requires. It
is a not infrequent characteristic of the bird family that each
species should have its own rather restricted diet. Birds are quite
particular eaters, and many of them will come well nigh to starvation
before they will use unaccustomed food. The sparrow, on the contrary,
like man, eats almost anything he comes across that could reasonably
be considered edible. He belongs to a group of birds which are
structurally adapted to cracking the hard coats of seeds. This group
of birds known as the finches is provided with the sort of bill
familiar in the ordinary canary bird. It is short, heavy at the base,
comes quickly to a point, and is firm and strong. With it the bird
readily breaks through the hard outer coat of most seeds and feeds
upon the rich cotyledons that are enclosed within. Nowhere in its
entire structure does the plant crowd so much nourishment in so little
space as it does in the seeds. It is not by chance that the great
human food is grain. The sparrow belongs to the one bird group that
makes a specialty of such seeds.

Most of the English sparrow's cousins in this finch group confine
themselves rather rigidly to this diet. Here the variability of the
sparrow again gives him the advantage. He may have the family fondness
for seeds, but in their absence he can be content with almost anything
edible. In the early springtime, when the seeds of last year are gone
and those of the new year have not yet been produced, the sparrow is
not averse to eating young buds from the trees. At this time he is not
unlikely to eat our sprouting lettuce and peas. It is easy to be
severe on him in this matter; but for a creature like man, who has the
same tastes, who eats the enormous buds of the cabbage, the
cauliflower, and the brussels sprouts, or the more tender buds which
he calls heads of lettuce, it seems particularly inappropriate that he
should throw stones at this little creature whose tastes are so
similar to his own.

While seeds are more suitable for an elder bird they are altogether
too indigestible to be the food of nestlings. So when the sparrow
finds its nest full we know he must sally forth in search of
nourishment more simple of digestion. Now for a few weeks he searches
assiduously, catching insects and caterpillars of various kinds, and
feeds them to his young. This taste passes as his children grow older,
especially as shortly the seeds begin to ripen. Now is the time for
the sparrow to fatten. Now he is eating the food for which he was
really built. By the time the wheat is ripe there are sparrows enough
about to form quite a flock, and when these settle down in a wheat,
rye, or oats field and feed upon the grain, meanwhile shaking out upon
the ground perhaps as much as they eat, the farmer begins to realize
that the sparrow is not his friend.

When winter comes the struggle for existence among the birds is
intensified, and comparatively few of them dare face it. Most of our
birds betake themselves to less rigorous quarters, leaving to the
sparrow a comparatively small number of competitors for the diminished
supply of food. As long as the snow is off the ground the sparrows can
find sufficient sustenance. They gather themselves into groups and
sally out from the city into the open country. The immediate result is
that great quantities of weed seeds are seized upon by the English
sparrow, as, indeed, by every other finch which is with us in winter.
Perhaps we have not given the little fellow credit for the good he
does at this particular time, for the rest of the account truly does
not help him in our esteem.

There is a further direct advantage in the sparrow's sociability. One
robin may nest in the vines about your porch. If there were room for a
dozen, scarcely more than one would be likely to use it, because he
would drive away any other robin who attempted to share the
neighborhood with him. To the sparrow company is always in order.
While he may quarrel from morning until night with his fellow, it is a
sociable quarrel and neither would willingly forgo it. This union is
strength among birds, as with man. Every animal is safer from his
enemies when he can have the constant presence of others of his own
kind. The deer that stays in the herd is safer from the wolves. It is
only when the latter succeed in cutting out some weaker or less
sagacious animal that these carnivorous creatures succeed in tearing
down their prey. I think the superiority of the sparrow over most of
our common birds, when considered as a city dweller, is scarcely
understood. Because he had won in the race with other birds is no
necessary indication that he warred directly against them. Bird-men
often attribute to him a quarrelsome disposition, as if he actually
drove other birds away. It almost seems like animosity against the
sparrow to speak of him as attacking blackbirds and crows. It is a
cowardly crow who can be driven away by a sparrow, and if the two
cannot live together it seems to me certainly to the discredit of the
crow and not of the sparrow. I believe the truth to be that, while
the sparrow is undoubtedly a quarrelsome fellow, his bickerings are
his form of social converse with those of his own kind. A quarrel
among themselves seems not to indicate animosity, but would appear to
be the sparrow's idea of conviviality. It rarely leads to serious
results. I have never seen a male sparrow trounce any other bird with
half the vigor that I have occasionally seen the mother sparrow evince
when she caught her male companion by the feathers of his head, hung
him over the side of the limb, and vigorously and thoroughly shook him
until he desisted from his annoying and possibly insulting attentions.
The truth of the matter is that a colony of these little birds, with
their continual social chatter, including their quarrels, makes such a
continuous noise that the ordinary bird, which is generally of rather
quiet disposition, is too much annoyed by the unending nuisance to
find the neighborhood at all to his taste. Where a large number of
sparrows have gathered together the conditions are such as would give
a robin or a bluebird nervous prostration, and his only recourse is to
depart to a neighborhood where there is more peace and quiet. But our
English sparrow is not only better fitted for the struggle than the
robins and bluebirds, the orioles and the wrens. He has one important
advantage over even his own sparrow cousins. The males are
handsome--much more so than the females or than their sparrow cousins
in general.

In the song sparrow, field sparrow, chipping sparrow, and the fox
sparrow the male and female are very nearly alike in color. It often
becomes necessary for the bird-man to examine the internal organs of
the bird he is stuffing before he can certainly decide its sex. But
there is no difficulty whatever in telling the male from the female of
the English sparrow. The male is far the more ornate bird. His back is
striped with a richer brown; his head has two splendid dashes of
chestnut over the eyes; his throat and breast are splashed with red
and lustrous black; his bill is a clear fine black. Altogether the
bird is strikingly colored for a sparrow, and this characteristic is
the more remarkable when we see how quiet and somber is his more
modest mate. This brilliancy of male plumage in the presence of the
somber color of his mate would seem to indicate that the English
sparrow is eye-minded rather than ear-minded. It is true among human
beings that most of them are eye-minded. That is to say, they notice
things with their eyes chiefly. Memories they have are memories of
things seen; recollections of their friends bring up the appearance of
their friends. Their language is full of metaphors which imply form
and shape. But occasionally we come across an ear-minded person. He
remembers voices quite as well as he remembers faces. To him music is
an unending delight, and painting and sculpture fall into a distinctly
secondary place. This is ear-mindedness. Now, most of the sparrows
seem to be ear-minded, at least as far as their recognition of their
mates are concerned. In this group beauty of song is developed many
times oftener than is especial ornateness of plumage. The bird-lover
who is himself keen of ear is never tired of listening, when in the
field, for the two low notes with which the vesper sparrow introduces
a song, the rest of which is not at all unlike the one of his
song-sparrow cousin. The field sparrow begins more like the song
sparrow, but ends with an often repeated note, which not a little
resembles in general character the somewhat more monotonous song of
the grasshopper sparrow or of the chippy. In comparison with these
melodious birds the English sparrow makes no showing whatever. His
voice is harsh and querulous, although very occasionally it is
possible for the bird-lover to detect a note or two which would
indicate that, if he were properly educated, his voice might amount to
something. He wins his wife not by his pleasant voice, but by his
attractive appearance and his winning ways. We have every right to
infer from the character of its fellow birds of the sparrow family
that once the female and male sparrow were colored about alike. But
Madam English Sparrow was apparently eye-minded rather than
ear-minded. Whatever pleasant voice a suitor might have seems to have
been to her without attraction, and there was nothing to encourage him
in developing it, nor was she likely to mate with him for it and
transmit it to her male children. On the other hand, let a suitor
appear in whom a more brilliant coloring proclaimed his superior
vigor, and this seems to catch her eye at once. The less accomplished
rival in the tournament of love seems to have been already forgotten.
To their children these successful characteristics were naturally
handed on and led to equal success on their part. If any of these
children possessed this badge of honor in a more than ordinary degree,
he was the more likely to win a mate and thus again the opportunity of
passing on to his offspring his own distinct advantage. Generation by
generation the males have become more beautiful and the females more
discriminating. That the bird is either instinctively or actually
conscious of this advantage would appear from the constant fluffing of
his feathers and spreading of his highly colored wings with which he
evinces his admiration for his ladylove. Even the most hardened
dweller in the city can scarcely have failed to see the sparrow spread
his wings, fluff his feathers, and sink close to the ground, twirling
and gyrating about the object of his affection. It must give him a
shock to see how often she proves temporarily or hypocritically
indifferent to the demonstrative proceedings. Indeed they may
terminate in a thorough trouncing of the male on the part of the lady
of his affections. Now this preference for color over song must have
evidently evolved in connection with the development of social habits
in the English sparrows. His cousins of the fields, our native
sparrows, are much less social, much less likely to be met with in
flocks. To birds who scatter more, beautiful song is a great
advantage. It can be heard at a long distance. But when birds flock
together a much better advantage is that of beautiful clothing, added
to alluring ways.

But we have not nearly exhausted the catalogue of the traits belonging
to our little friend which give him the advantage over other birds in
the struggle for life. His ability to remain with us in winter when
most birds are gone stands him in good stead.

It is readily observed by one who pays the least attention to outdoor
life that winter finds us with comparatively few birds. North of
Maryland and the Ohio River the robin is practically absent in the
winter, except in much diminished numbers close to the border. The
bluebird is similarly absent; the great flocks of blackbirds are gone;
the bobolink is missing entirely; the thrush and the catbird have all
left; the flicker and red-headed woodpecker are also spending their
winter in the South. The great mass of our bird population has left us
until warmer weather shall bring back to us once more our feathered
friends. It is true that we are south to the snowbirds or juncos, and
their little slate-colored bodies, with their light breasts and their
white on each side of the tail, make our bare hedge rows brighter by
their presence. A few of our birds like the song sparrow and the
cardinal are hidden away in the thicket, and have not all joined their
comrades in the south.

The English sparrow was once probably quite as migratory as any of the
rest of these, but a great change has come over his habits. With his
newly acquired fondness for the haunts of men he has suffered a change
in this respect also. Whatever may have been his reason for migrating,
it no longer holds. He now finds himself quite able to stand the cold
of winter. Accordingly he never leaves us, except very temporarily.
When the migrating season comes the sparrows of the neighborhood are
very likely to gather themselves together in a single group and take
to the neighboring country. I believe this flocking on their part at
this time of the year is a remnant of the old migratory habit. Until
snow covers the ground the sparrow is not likely to be seen again in
such numbers in the city. The advantage the sparrow gains over his
competitors by not going south does not appear during winter. When
spring comes, however, his gain is evident. He has his choice of all
the nesting sites in the region. When the migratory birds return every
first-class place is filled by a sparrow's nest. Nothing but second
choice situations remain, and with these the late comers must be
content. When we consider how much the safety of the next generation
depends upon the security of the young while helpless in the nest, we
appreciate what the English sparrow has gained by staying throughout
the year. Often while the season is so inclement that it would seem
there is still danger of frost, the sparrow builds her nest. All sorts
of places are open to her choice. She will find a protected corner
under a roof, above a spout, in the corner of the porch, behind an
open shutter, in the vines against the side of the house, on top of an
old robin's nest in the tree, in the bird boxes which have been put up
for more desirable creatures; anywhere and everywhere this industrious
little mother is liable to build her nest. Her husband will help her
more or less in the task, often bringing material and helping to place
it in the negligent pile of which their nest is composed. But he does
a good deal more fussing and cheering up than he does actual work, and
she seems to depend much upon his cheerful presence for her happiness.
It is hard to discourage Madam Sparrow when once she has set her mind
on home-making. A bird-lover, some time since, reported how a pair of
sparrows had started to build a nest upon his lawn. He, wishing to
interfere with the process, took a small rifle and shot the male bird.
Within twenty minutes the female, who had scouted round the
neighborhood, returned with another mate and resumed her nest-building
process. Again he interjected the tragic note into her life by
shooting her second husband, only to find her start out in pursuit of
a third, with whom she returned in the course of an hour. He felt that
by this time he had interfered with her domestic happiness as much as
he had any right to do, and suffered her to continue her housekeeping
with her third husband without further molestation. I imagine it would
have puzzled both birds to tell who was the father of the nestlings
who appeared two weeks later.

Not only do sparrows nest early, they nest often. I suggested to one
of my students that she locate as early in the season as she could the
nest of a pair of English sparrows, which was sufficiently accessible,
and that she keep it under observation at intervals of a few days
throughout the summer. In the fall she came to me with glowing eyes
and gave me her report. "It is simply great," she said. "I never went
to that nest a single time this summer to find it empty. When I first
got there I found four eggs; after a while these hatched out, and the
young were on the nest until they were old enough to fly; but before
they had left she had slipped a fresh egg among them, ready to start a
new batch. Whenever I saw the nest throughout the entire summer, I
found in it either eggs, or young, or both." Such reproductive energy
as this is hard to beat; compared with this rate of increase, the
ordinary bird is the exponent of race suicide. How can a robin hope to
compete with this family industry? What can a bluebird offer that will
approach such chances of a worthy successor when his work shall be
finished?

These, then, are the most important points in which the English
sparrow has varied from his sparrow cousins and made of himself the
most successful town dweller in the bird world. He has become clannish
and gained the advantages of coöperation. He has used man's highways
and cars by means of which to expand his area. He has cultivated the
presence of man and thus gained protection from his enemies, food from
man's waste, and nesting sites on man's house. He has assumed a varied
diet. The male has become handsome. He has given up migrating, and
thus secured the best nesting sites. He has learned to produce many
offspring. With all his versatility, why should he not succeed?

Thrown into competition with our native birds, he easily beats them
on their own ground. He survives against the competition of birds
which seem to us more estimable in every way. The very fact that he
survives proclaims his superiority over them, and shows that our
criterion is not the one by which nature judges. We like the birds
which serve our purpose. We admire the brilliant plumage of the jay,
cardinal and goldfinch. We love the mellow notes of the woodthrush,
and of the veery, the clear, rollicking outpourings of the bobolink,
the musical love song of the brown thrasher, the cheerful scolding of
the wren. We are fond of the birds who busy themselves taking the
insects out from among our grain and from off our fruit trees. We can
only understand the value of the bird to nature when he is valuable to
us. So, because the English sparrow does little that is to our
advantage and much that is to our annoyance, he is in our estimation a
reprobate and an unending nuisance.

All sensible bird-men must clearly acknowledge that he is a very
undesirable citizen. I write the above sentence to show that I realize
the whole duty of the bird-lover in the matter of the sparrow. This
pestiferous creature should be exterminated by traps, by grain soaked
in alcohol, or strychnia, by fair means or foul. But personally, I am
taking no share in his destruction. Any bird-lover, after reading the
foregoing account, can scarcely have missed the undercurrent of my
affection for the little rascal. He is a thorough optimist; he is
absolutely persistent; no hardship seems to dampen his ardor. His
heart is valiant above that of most birds so that he has dared to make
of man his near neighbor when other birds consider him their worst
enemy. I love him for it. When I am in the midst of a big city with
its cliffs of offices and its gorges of paved streets, it is to me a
cheer and a delight to see this happy little fellow who has adapted
himself to circumstances against which no other bird, excepting the
pigeon, can cope. I confess that it would be with regret that I should
see him disappear from the landscape. I have missed a long line of
spring peas through his ravages, and he has objectionably decorated
many places about my own home. But I have yet the first violent hand
to lay upon the sparrow, and I doubt whether my hand is ever to be
reddened with his blood.

I am going to ask bird-men to forgive me if I say that I believe,
although I speak only from general impression, and not from careful
research, that the sparrow within the past eight years has reached his
equilibrium in the neighborhood of Philadelphia and is growing no more
abundant. Meanwhile another and very desirable state of affairs is
arising. Bird love and bird protection are so active in this
neighborhood that there is growing to be a new race of birds who lack
the fear of man their ancestors justly had. Under these conditions the
wild birds, which for a while we believed to have been completely
driven out by the sparrow, are rapidly returning to our villages and
towns, and we have many more robins and catbirds, wrens and flickers
than we had ten years ago. We have seen the worst of the English
sparrow; he has now found his equilibrium.



CHAPTER IV

ADAPTATION FOR THE INDIVIDUAL


Among the standard books of the classical curriculum in the
denominational college of thirty years ago was a volume which I
suppose has practically disappeared from such courses. It delighted
many of its students for a reason entirely different from that which
the author meant should be its taking feature. It was Paley's "Natural
Theology." The author started with a story of a watch found by a
savage. This child of nature was supposed to examine its mechanism and
to infer that the watch was made for a definite purpose. As I
remember, he was even supposed to discover that its purpose was to
mark time. It was at least to become clear to his savage mind that
this was no chance object, but was the definite product of a designing
mind. Having brought this hypothetical savage to these conclusions,
the author turned himself to savages nearer home who fail to see
design in nature. The book takes up a great many cases of interesting
facts in animals and plants as clearly showing evidences of design as
did the watch our savage picked up. But the inference we were expected
to draw was that the design shown in nature argued clearly for a
Designer above nature; in other words, that nature was unintelligible
without God. Everyone in the class believed in God without this
preliminary, and consequently the book was unnecessary, so far as we
were concerned. We started with the condition of mind which the author
hoped to produce. One effect the book did have; in the absence of any
other reputable course in zoölogy, it gave us an astonishing
collection of interesting facts about animals.

Some of Paley's statements were certainly peculiar. His Malay pig with
its upper teeth wonderfully curved was said to be in the habit of
hanging its head upon a bush while it slept, in order to save the
strain upon its porcine neck. This was too much even for our
credulity. None the less the impression made upon some of us by the
evidence for design in nature has never left us.

Among many scientists to-day it is supposed to be crude to speak of
purpose in nature, and there is reason for their attitude. But the
statement that there is no such plan conveys to the ordinary thinker a
meaning that is far more erroneous than could possibly exist in his
mind should he believe implicitly in design and purpose. As between
design in the universe in the usual sense of the word, and a purely
accidental connection of events in the universe, there can be no
doubt as to the choice. The truth is far better expressed by the word
design than by the chaos which is the alternative idea in the average
mind. In these later years we have come to use a different word. We
now conjure in such connection with the word adaptation. In every
animal and every plant the trained eye sees unending examples of
adaptation; that is, of a fittedness to the work it has to do. The
modern scientist feels sure not only that the animal is fitted to his
work, but that he has been so fitted by the work; that the very use he
makes of his organs has determined their structure. This work has
decided that the structure which he has is the structure that shall
survive and shall produce other structures like itself. Adaptation
therefore does not simply express the idea that the animal is adjusted
to its surroundings, but it further suggests that the animal by
gradual process has become thus adjusted. The word adaptation applies
not simply to the result, but also to the process. The scientist does
not consider the animal a final and complete result. He thinks it
still in a state of flux, and so long as its line lasts it will be in
a state of flux. Change is about it on every side, and it must adapt
itself to this change or it will pass away. It may adjust itself, as
has been previously stated, by moving to another environment in which
it feels more at home, but unless it does this, if there come much
change in its present surroundings, it must either meet the
difficulty by altering itself, or it must give up the struggle. The
alteration is unconscious so far as the animal is concerned. It is
seriously to be doubted whether there is any recognition of the
process on the part of any animal excepting man. But though the
process be unconscious, it is none the less there. Slowly and
gradually the animal and the environment are becoming adjusted to each
other.

While it is exceedingly difficult to lay our hands on any animal which
is at present visibly changing its structure, it is not hard to find
closely related animals. These are nearly alike in structure in most
respects. In a few points, however, they may differ materially, and
these points are often directly concerned with different habits of
life. Considered in this aspect, these adaptations of a single organ
separately examined form an excellent argument in favor of that
gradual alteration of the entire organism which evolution suggests.

The most primitive struggle in which an animal can possibly engage is
the effort to maintain its own life and vigor. This struggle will
result in certain adaptations for the individual, adjustments which
make for the safety of the animal himself. These form the subject
matter of the present chapter.

The farther up the animal kingdom we pass in the study of adaptation,
the more likely we are to find changes which have but little bearing
on the safety of the individual. They work for the good of the entire
species, sometimes to the distinct disadvantage of the individual. The
King Salmon may make its long run to the headwaters of our western
rivers, deposit its eggs, have them fertilized, and then float down to
death. But it does not die before abundant preparation has been made
for the continuance of the race. Such adaptation for the good of the
species will be considered in the next chapter.

The first and most important struggle any animal has to enter is the
never-ending battle for its food. Occasionally there is a similar
straining after the air it breathes. But ordinarily air is
sufficiently abundant, except to animals living in the water, where
the supply is always more or less restricted and easily becomes
exhausted. But food is the constant need of every organism, and most
creatures die for lack of it. In this struggle the animal is pitted
against those of his own kind, rather than against those of other
species. Even his brother is his enemy, for he desires the same food.
In many a nest of birdlings one of them fails to reach its development
simply because the parent either is unable to find or it cannot carry
enough food to satisfy all the hungry mouths in the same nest. Before
the nestlings are ready to take their place in the struggle for life
outside and hunt their own living, one or more of them has succumbed.

After the battle for food comes the struggle for shelter. For most
animals there is no such thing as shelter. They are exposed to the
inclemencies of the weather and to the depredations of their enemies
without the means of retiring into any situation which might protect
them. In the higher animals, especially when they are warmer blooded
and their bodies must be kept at a higher temperature, some form of
covering has come to be almost universal.

Though comparatively few animals are prepared to seek shelter from the
cold, all of them have enemies against whom they must battle. These
foes may wish to eat them or may simply wish to get them out of the
way. In either event this struggle is so persistent and so keen that
after starvation it is probably the source of the largest loss to the
animal kingdom.

Considering first the feeding habits of animals, we find they are
exceedingly varied. Some creatures simply engulf other and more minute
animals, often only microscopic in size, in such quantities as to
satisfy their hunger. Others, feeding upon larger plants or animals,
must have some means of breaking off particles of this food; still
others confine themselves entirely to nutritious fluids, and must have
organs adapted to this particular type of food.

Insects are so common that anyone, who cares to, may easily verify
what is here described. It will take nothing but a clear observant eye
and a little patience to make out what is suggested. Each of our
common insects has one of two clearly defined habits in the matter of
food. Either it eats solid food, which must be made fine before it can
be taken into the mouth, or it feeds upon liquids. These liquids may
be easily accessible like the nectar of flowers, in which case one
sort of mouth will serve; or they may be the juices inside the tissues
of animals and plants, when an entirely different type of mouth must
be employed in their acquisition. Perhaps the most easily found
representative of the biting type of mouth, which breaks up solid
food, will be seen in the common grasshopper. Doubtless each one of my
readers has at some time taken a grasshopper into his hand, and,
holding the tip of his finger against the insect's mouth, has promised
the creature its freedom on condition that it disclosed its
reprehensible habit of chewing tobacco. The grasshopper surely
complied, and I trust the promiser was as good as his word. The
grasshopper's head is so placed that, while it is at the front of its
body, the mouth is directly on the under side of its head, while the
eyes are at the top of the front of its face. Under these
circumstances it cannot see what is going into its mouth, and this
makes an interesting variation of conditions to which it must adapt
itself. The means by which it accomplishes this will be clearer if the
mouth of the grasshopper be compared with our own. Our lips are upper
and lower, but the grasshopper has a front lip and a hind one. The
broad front lip is easily seen at the forward side of the mouth. Just
behind it, serving the purpose of our teeth, is a pair of hard jaws
with horny tips upon them, which serve to break small pieces from its
food. While our jaws and those of all other backboned animals work up
and down, so that we may be said to have an upper and lower jaw, the
grasshopper and all of his insect, crab, or spider relations, which
have jaws at all, have them right and left, and they work from side to
side. Behind these harder mouth parts is found a pair of softer jaws,
each of which has on it a little finger-like feeler. With this pair
the insect holds its food while the hard jaws break it to pieces. The
hind lip follows, and is also provided with short finger-like feelers.
The feelers on the hind lip and on the soft jaw are necessary because
the eyes are so placed as not to be able to see what goes into the
mouth, hence the insect must make up for the loss of sight by the
addition of touch. The same type of mouth as the grasshopper has will
be found among the beetles. Here the males sometimes have the hard
jaws so enormously enlarged that they are known as pinchers and have
given to their owners the name of pinching bugs. All insects with such
jaws as these use them for breaking up solid food.

A glimpse at the mouth of the butterfly captured on an adjoining
flower will show a most remarkable variation from that seen in the
grasshopper. Practically all of the mouth parts mentioned are present
in this insect, and its early ancestors had their organs practically
like those of the grasshopper. Now they are so modified and united
with each other as to be almost unrecognizable. The pair of soft jaws
has become very much elongated, and they lock together in such a way
as to enclose a hollow space between them through which the creature
can suck its fluid food. Not only have these soft jaws joined
together, but, because they have become so much elongated when not in
use, they must be coiled up like a watch spring and laid between two
hairy lip-like processes which correspond in reality to the two
finger-like feelers of the grasshopper's hind lips.

The butterfly, lighting upon the corolla of the flower, uncurls this
long "tongue," and through its hollow center pumps up into its crop
the nectar which the flower has stored in its base. When the butterfly
comes to get the nectar from the flower, it rubs upon its own hairy
body pollen from the stamens of the flower and carries it to the
pistil of the next flower of the same kind which it visits. Most of
us have at some time sucked the nectar from the back of a torn
honeysuckle blossom and approved the taste of the butterfly in this
matter. If the airy creature be watched as it lights upon a flower, it
will not be difficult to see it uncurl this long tongue and probe the
depths of the flower. If the butterfly be taken in the hand and the
tip of a pin inserted in the center of the coiled tongue, it can be
uncoiled without the slightest harm to the butterfly.

Insects which wish to use for their food the juices of other animals
or of plants do not find them so easy to gather. In the mosquito most
of the mouth parts are developed into slender pointed bristles wrapped
in a hind lip. These bristles serve to puncture the skin of the
creature attacked, while the curled lip serves as a tube through which
the blood may be extracted.

If, while sitting on the porch on a warm summer evening, mosquitoes
begin to annoy, let one of them at least serve to show his method of
procedure before he is destroyed. Allow the creature to alight upon
the back of your hand and slowly raise the arm until the eye looking
at near range can see the head of the mosquito, which, by the way, is
sure to be a female. Males in this species are entirely harmless. They
never eat after they have grown up; that is, after they are truly
mosquitoes. But the female is very assiduous. Alternately raising and
lowering her lancets from either side, she pierces, then saws, her way
down through the flesh until she has buried her instruments in her
victim and her head rests against her prey. Now a pumping motion of
the abdomen will be apparent, and this continues its accordion-like
action until it becomes more and more distended. The insect only gives
up its task when the entire abdomen is swollen into a great red ball
of blood. The mosquito will now slowly withdraw its instruments and
retire from the scene, if permitted to do so. If there is any fear of
annoyance from the bite, a drop of ammonia immediately applied will
counteract any irritation which would have been produced by the saliva
of the mosquito. The insect is not intentionally vicious in this
procedure. It is simply gathering its own natural food, though this
does not make it less annoying to us since we are its victims. The
swelling produced after the bite is the result of the action of the
saliva the mosquito injected into the wound. The opening through the
tongue is so small that blood would readily clot inside the tube and
prevent its further usefulness, did not the mosquito inject the
secretion of its salivary glands into the wound. This acts upon the
blood in such a way as to prevent its coagulation.

Anyone who thinks carefully can add numberless specializations for
food getting. For instance, primitive mammals have little pointed
teeth which fit them for feeding on insects. In each of the great
order of mammals a special development of these teeth has occurred.
Among the rodents or gnawing animals the front teeth have become long
and chisel-shaped for nibbling. The horse has formed them for nipping,
and his hind teeth for grinding. In the dog the teeth near the front
have become long for tearing his flesh food, while his hind teeth,
working with the motion of scissors, cut it into pieces.

A second great class of specialization is seen in the changes of habit
that provide the animal with shelter. The home seems so necessary a
part of human life that it is almost impossible to think of an animal
having nothing that in the faintest degree could be called a home. We
at least expect it to have some sheltered place in which it passes
most of its time and to which it returns after its wanderings. The
great majority of all animals have no such home. The place in which we
find them to-day may not be the place in which they will be to-morrow.
All places are alike to them. The ordinary conduct of their daily life
drives them about in the search for food. Their attempt to escape from
their enemies leads them each day into new situations, and they may,
and probably do, have no power to recognize the old location if they
return to it. When we come to the backboned animals there is a little
more tendency to a stationary location. The sun fish may frequent the
same reach of the stream, the trout may haunt the same pool, year
after year, but a great majority of fishes doubtless move
indiscriminately up and down the stream or about the lake or ocean and
are not found two successive days in the same place. The same may be
said of frogs. For a time a particular frog may have a fondness for a
special bend in the stream, but it is only a temporary fondness, I
believe.

Our own need for shelter is the prime motive in leading us to build a
home, and this necessity arises first of all because of our warm
blood. What we are accustomed to call cold-blooded animals are not
truly so. Their blood holds practically the temperature of their
surroundings. As the air or the water in which they live grows warmer
or colder the bodies of these creatures alter with it. Consequently
they are active when the temperature is high and grow more sluggish as
the thermometer falls. When the day grows distinctly cold the animals
may go practically dormant.

Only the birds and mammals have warm blood, and of these the birds are
distinctly the warmer. Whereas the temperature of the mammals runs
from about ninety-eight to a hundred degrees Fahrenheit, that of
birds lies somewhere between one hundred and five degrees and a
hundred and ten. Creatures which are warmer than their surroundings
must have some protection against chilling. Accordingly both mammals
and birds have clothing. In the case of mammals the covering is fur,
in the case of birds feathers. In some of the tropical animals like
the elephant and rhinoceros, or in man, who has learned to protect
himself in cold regions by making clothing for himself, this hair is
very short, and except where serving for ornament is quite scanty, no
longer being of use as a protection. But the great majority of all
mammals are well covered with a dense coat of hair. In many of those
living in the colder regions there is in reality a double coat. The
fur seal of the Alaskan Islands is so provided. A set of long hairs
deeply fastened in the skin forms a covering, which shows on looking
at the seal. Underneath this layer, and set but lightly into the skin,
is a short coat of very much finer hair known as the underpelt. When
the skin is taken from the seal it is split by machinery into a lower
and an upper layer. When so split the deep-seated pits of the long
hairs are cut, and these hairs come out. The fine underpelt thus laid
bare is what is commonly known as sealskin. Fashion has decreed that
this must be dyed a rich brown, although when taken from the animal it
is nearly mouse gray.

The birds have need for better clothing. To begin with, their blood is
much warmer, and hence needs better protection from outside cold. In
addition such of them as fly high must be prepared to stand great
variations in temperature. For these purposes birds need a covering of
the finest type. This clothing, in addition, must be extremely light
because the creature must carry it into the air in flight. All of the
requisite conditions are thoroughly met by the feather, which is the
lightest and warmest clothing known to man. If at night we wish,
regardless of expense, to keep ourselves warm with the lightest and
warmest of covering, we send to the Arctic Sea, and from the breast of
the eider duck we pluck the down which lies between the warm blood of
the duck with its temperature of one hundred and seven degrees and the
water in which the iceberg floats.

Young mammals and birds, before their clothing has well formed, are
naturally susceptible to cold; this leads to the first genuine
approach to a home among animals lower than man. Birds lay their eggs
long before the creatures inside of them are ready to emerge.
Accordingly they have learned to build nests in which to place these
eggs, and to protect them from the outside air; meanwhile the bird
keeps the eggs warm by close contact with its own body. The lowest of
the birds may lay their eggs simply on the ground without any special
protection. As we rise in the scale of the bird world we find nests
provided for the eggs. These nests become increasingly complex and
specialized, until we reach the oriole's home with its wonderfully
woven mass of fiber, which, in spite of its apparent looseness,
supports well the weight of the mother bird and of her eggs. The
robin, not content with making a woven basket, plasters it with clay,
and makes an absolutely impervious nest.

When we remember that both mammals and birds are the modern
descendants of cold and scaly reptiles of an earlier geological time,
it becomes interesting to compare their clothing. Evidently in the
mammals hairs began to come out between the scales. Gradually the
scales became fewer and the hairs more abundant until finally the
scales have all disappeared, except those that remain as the claws on
the toes. The ancestors of the birds, on the other hand, boldly
transformed their scales into feathers.

Another need for shelter arises in connection with the approach of
winter. This problem of withstanding the cold season is complicated by
the presence of two new factors. First and most directly, the cold
itself is a distinct obstacle to the comfort of many of these
creatures; as a secondary result of this cold, the food of many
animals disappears entirely in winter. Most of our birds meet this
difficulty by changing their base of operations. When the north grows
cold these creatures fly to the south. Some of their migrations cover
enormous stretches of country. Our bobolink, so well known and loved
by all watchers of spring migrations, passes twice a year between the
latitude of New York and Rio Janeiro. One of our most careful students
of bird migration says that the Golden Plover makes, twice each year,
the long journey from the Arctic shores of North America to the plains
of La Plata.

Different fur-covered animals have specialized to meet the winter by
any one of three different methods. They may brave it out, hunting for
their food as best they can all winter long. Such a course is pursued
by the rabbit. Again like the squirrel, they may store large
quantities of food during the summer, and on this provender they may
subsist during winter, remaining for most of the time near their
hiding-places, which, however, they may frequently leave upon warm
days. A third method is less common, but very interesting. The
groundhog or woodchuck is the best-known example of the group. It
remains asleep, or, as it is technically known, dormant, during the
winter. This stupor is more profound than ordinary sleep, and from it
these animals awaken with difficulty. It is needless to remark that
the groundhog's behavior on the second of February has no relation
whatever to the weather we are to have later in the season. This is
coming to be pretty generally understood. While the newspapers each
year comment upon the groundhog and his shadow upon that day, year by
year the notice has more of humor in it, and fewer people pay any
attention to it.

As for the backboned animals which are cold-blooded, these must,
unless they are fish, give up the struggle completely, bury themselves
in out-of-the-way places, and go worse than dormant. They often become
absolutely cold and stiff. In the case at least of fish, it is quite
possible for them to be frozen stiff, even to be enclosed in cakes of
ice, and still to recover if the encasement is not too long continued.
But the snakes, the turtles, the toads, the lizards, all are hidden
beneath the ground waiting in absolutely unconscious rest the return
of warmer weather.

After the need for food and shelter comes the continually recurring
necessity on the part of almost every type of animal to escape from
the unwearying persecution of higher creatures which would feed upon
it. The whole creation is a constant network of animals which prey
upon each other. It is the fate of a great majority of all creatures
to fall victim to other animals to whom they serve as food.
Accordingly nature has concocted many devices by which she assists
her favored children in escaping this relentless persecution. Perhaps
the most widespread means which animals have developed in order to
elude their enemies lies in the possession of power to escape their
attention. Two different factors may contribute to this end. The first
of these consists in the practice on the part of many animals of
remaining absolutely quiet in time of danger. This instinct seems to
be nearly universal. The first impulse of most animals upon
discovering danger is to remain absolutely motionless. The eye
detects, with ease, objects in motion. These same objects might
entirely escape attention were they quiet. A mouse could remain in the
corner of a room for a long time without attracting the eyes of the
occupants of the room. Let it but scamper across the corner, and at
once it is discovered. It is quite conceivable that early animals were
divided in the matter; that the impulse of some was to escape from
danger, while others, frightened by the presence of the enemy,
remained absolutely still. Each plan has succeeded. Those which, on
running, ran fast enough to escape became the parents of others like
themselves, led eventually to a line of animals in whose speed lay
their safety. Those, however, which attempted to escape, and failed
because they were not swift enough, had their line cut off, and were
thus less likely to be represented in the following generation. The
constant result of errors along this line would be to destroy the slow
and preserve the swift, and in the course of time it is quite
thinkable that only the swift should remain. As the movements grew
more and more keen, even the slower of these would pass out, thus
tending always to produce the succeeding generation from those who
were most rapid, and hence most likely to transfer to their children a
similar power.

But there is another tendency of animals which leads them when
frightened by their enemies to remain quiet. If this impulse is obeyed
thoroughly enough, it is easy to see how the owner of this habit might
entirely escape detection by his enemy. Any restless animal unable to
restrain his nervous agitation naturally betrays his presence and is
picked off. The result of evolution along this line would be the exact
reverse of the preceding. Those that lay most absolutely quiet would
be the parents of succeeding generations, while those who were slow in
coming to rest, or were indifferent about remaining quiet, were picked
off, and their tendency eliminated from the future of the species. In
this way many animals have come to keep entirely quiet in the presence
of danger. It is not a sign of high intelligence. As a matter of fact,
it is rather a stupid procedure, so far as the animal itself is
concerned, but it is a preserving stupidity, and many animals have it.

The "June Bug" (which is not a bug, but a beetle, and arrives in May)
has this interesting habit of keeping quiet. If in its flight it
strikes the globe of an electric light, it falls at once to the
ground, and remains perfectly quiet for a time. After a short interval
it recovers and starts out to regain its previous activity. But this
recovery is by slow stages, and the whole procedure on its part looks
exceedingly stupid.

The little snake with flattened and expanded head, known as the
blowing viper, or puff adder, is one of the most amusing
representatives of the tendency to "play dead" that could well be
found. If you strike him the faintest blow with the lightest stick, he
at once goes into apparent convulsions, in which he seems to suffer
the greatest agony. Then, throwing himself upon his back, he, to all
appearances, yields up the ghost. If, however, you retire but a slight
distance and keep your eye upon him, you find that his ghost returns
after a comparatively short absence, and he slinks away out of danger.
This is the most effective exhibition of this kind with which I am
acquainted.

As for the habit of "playing 'possum" on the part of our opossum, the
trick would seem to be particularly inane. The truth of the matter is,
what is attributed to an unusual brilliancy on the part of the
creature is positively unusual witlessness. The animal has an
exceedingly small brain, as compared with that of a dog of similar
size, and to anyone who knows brains at all this particular organ
would not be looked upon as furnishing its owner much ability. The
fact is that the opossum has exceedingly small wit, and this little
deserts it in an emergency, as a result of which he grows helpless and
motionless. This is often supposed to indicate great wisdom. There may
be wisdom in it, but it is the wisdom that lies back of all nature. It
certainly is not the wisdom of the opossum.

Man himself possesses to a marked degree this impulse to keep quiet in
danger. The man from the country who is visiting the large city,
suddenly startled by the "honk" of the auto horn, finds his power of
movement promptly arrested, and he is not unlikely to be struck and
injured by the machine from which the city dweller would easily
escape. This is not particularly to the credit of the city dweller,
who, when in the country, may find himself similarly startled by the
sudden appearance of the calf, the pig, or the sheep. The bull, which
a country boy, accustomed to him from childhood, will drive with a
willow switch, is a source of terrified concern to the city man.

While the trick of keeping quiet serves many an animal in time of
danger, there is another device for escaping attention, far more
common and widespread throughout the animal world. The eye does not
easily see an object if it is colored like the background against
which it stands. A host of animals find their main safety in being
indistinguishable in color from the surface on which they live. There
are many biologists who seriously question whether protective
coloration, as Darwin called it, is as effective as he believed it. In
some quarters it is the present fashion to doubt protective coloration
entirely. No one has yet shown any principles which will better
explain the great color scheme of the animal world, and until such
explanation is forthcoming I believe it will not be wise for us to
discard the idea of protective coloration. No doubt it has been
overworked by enthusiastic believers in its efficiency. At the same
time, to overlook it completely, is, I believe, to make a greater
error. I have little doubt that when the broader explanation comes,
which will satisfactorily explain the color scheme of the animal
world, the idea of protective coloration will be found, not so much to
have been wrong, as to have been but partial. It will be included
under the broader principle which takes its place and will not be
supplanted by it.

The idea of protective coloration is that very many animals have
ordinarily come to be colored like the background on which they live.
The process has taken many generations, and is very slow, but is none
the less sure in the end. In most cases the animal is probably
entirely unconscious of this point in its favor, and usually it does
nothing to assist the deception. The result is none the less effective
because the animals themselves are unconscious of the process. The
cabbage worm is green in color like the cabbage. This does not mean
that it got green by eating cabbage or by longing for greennesses.
Through long years the enemies of the cabbage worm have been picking
it off the plants on which it fed. This does not imply that cabbages
as we know them are very old, but cabbage worms doubtless ate the
leaves of the sea-kale long before man had cultivated it into cabbage.
During all these years the enemies of the caterpillars, generally in
the shape of birds, have been assiduously gathering them up.

When we see how much the various members of the same human family may
differ in complexion, how much the various pigs in the same litter may
differ in size and in coloration, it is easy to understand that among
these caterpillars which have eaten the cabbage there must have been
considerable color variations. I do not imagine for a moment that the
birds had any preference for any particular color in their cabbage
worms. They took every caterpillar they saw, but they naturally first
saw those that were least like the background on which they lived.
The only caterpillar which was effectively hidden from his enemy was
the one that was indistinguishable on the leaf. If it escaped in this
way, the probabilities are that it would produce young which would be
at least a little more likely to be green in color than the progeny of
its darker-colored brothers and sisters. By this continued process the
birds steadily weed out the darker-colored specimens. There would
result, in the course of time, a race of caterpillars, whose ancestors
for so many generations back had been light green in color, that there
is little likelihood of any of the older and darker forms turning up
again. In the course of time all dark tendencies will have disappeared
from the family and practically all of the group will be light green.
Any sport or variation in the shape of greater conspicuousness would
fall a quick prey to the enemy and its line be cut off forever.

The same sort of activity has resulted in the peculiar green color of
the katydid. This creature lives chiefly upon the leaves of trees and
shrubs. This insect is so large that, even though it is leaflike in
color, it might still be conspicuous. As a result those katydids whose
wings were most like leaves in form were least likely to be picked up
by the passing bird. This sort of protective appearance is intensified
by exactly the same means as that which brought about protective
coloration. The katydid least leaflike in appearance was eaten first.
Thus those most leaflike remain until the last, and are most likely to
produce young. Again, it was not the fact that they lived among leaves
which made them look leaflike, but it is because they look like leaves
that they escaped being devoured.

The katydid has materially assisted in its own preservation by being
active chiefly at night. In the daytime it keeps comparatively quiet.
Thus seated upon a twig, especially if hidden among the leaves, it is
almost unnoticeable. At night, however, it moves about more freely,
seeking its food and eventually its mate. At such times it becomes
distinctly more conspicuous because its wings are steadily fluttering.
The hind wings are filmy and are very light green. The creature looks
most ghost-like as it flies through the evening air.

A very similar history lies back of the coloring of the ordinary toad.
Though descended from the frog, and originally a creature of the
water, the toad has long since adapted itself to live upon the dry
ground. It still produces its young in the water as it did when a
frog. Whereas the childhood of the frog, that is, its tadpole stage,
is very long and it assumes its adult form comparatively late, just
the reverse is the case of the toad. The young hasten through their
tadpole stage within a few weeks, and assume the shape of the parent
toad when about big enough to cover your little fingernail. Now they
leave the water and seek dry land. Naturally they make the change when
the land is damp, that is, after a warm spring rain. People seeing
these multitudes of little toads hopping around over a bare spot of
ground, and remembering the rain of the night before, insist that it
has rained toads. Of course it never rains down anything which cannot
evaporate up. The stories of showers of toads and of earth worms, with
an occasional fish, or even creatures of larger size, are all pure
myths. There are conceivable tornadoes after which there might be a
shower of such creatures, but at such a time it is likely also to rain
barn roofs and buggies. You may be sure that toads which come down in
the rain are dead after they strike the ground.

The little toads started out, perhaps a hundred at a time, from the
small pool in which their eggs were laid. These creatures find dragons
on every side. The gartersnake comes along and gets his first toll;
the heron follows him and takes such as catch his hungry eye; the
turkey gobbles up his from what are left. By the time the toad-eating
creatures in the neighborhood have taken such as they found, there are
very few remaining. These doubtless have been left for a very good
reason, generally because they were not noticed. This was because they
looked like the ground on which they sat, and because they kept
perfectly quiet while the enemy moved about. This process has gone on
so long that the toad has come to be astonishingly well protected by
its resemblance to the ground. This likeness it intensifies by its
interesting habit not only of keeping entirely quiet, but of dropping
its nose to the ground, instead of sitting high on its front legs, as
it does when not in danger.

I have noticed that if a snake and a toad be placed in the same cage,
when the snake approaches to capture the toad the toad drops into a
squatting position, and is very likely to blow himself up until he is
rounder in outline than he was before. Whether this is a deceptive
trick which makes him the more resemble a stone is more than I can
say. I do not remember having seen our eastern toad do it. I have seen
it happen a number of times in the laboratory of a Colorado
naturalist, and it is quite possible that in the open country more
sparsely covered with vegetation than is our ground in the east this
inflating device may serve the toad more effectually than if it kept
its own outline.

Even among creatures far more active than the toad and the katydid an
inconspicuous color must certainly result in distinctly better
protection. Everyone knows the jay and the cardinal when first he has
seen them, if only he has a slight acquaintance with their pictures.
They are so conspicuous that we recognize them at once. More common in
my region than the jay or the cardinal is the red-eyed vireo. This
creature moves industriously in and out among the leaves of our trees.
It is persistently in motion, is nearly constant in song, and is a
bird of fair size, being larger than our English sparrow, though
smaller than a robin. Many a nature lover will recognize twenty-five
or thirty birds at sight without any difficulty, and not know the
vireo. Yet the vireo is more common than two-thirds of the birds he
knows. There can be but one reason for this; the bird is
inconspicuous. The olive-green of its back, with its light under
parts, serves to hide it completely amid the foliage. Even the
bird-lover learns to find it first by its jerky song, and then by
watching for its movements among the leaves.

One aspect of protective coloration has been brought to our attention
by the artist, Mr. Abbott N. Thayer. He first clearly explained why it
is that animals are usually so much lighter on the under side than
they are upon the upper. Mr. Thayer proves his position by taking some
ordinary cobblestones and painting one of them a uniform color and
placing it upon a board painted the same color. One would think the
stone would be inconspicuous; as a matter of fact, is quite easily
seen. The underside of the stone, turned away from the light, is so
shaded as to mark a distinct boundary between the stone and the board.
Another cobblestone was colored on its upper side like the board, but
the color faded into a lighter and lighter tint until the bottom of
the stone was nearly white. This stone, placed upon the board, was at
a short distance nearly invisible. In other words, although the
pigment was actually lighter on the under side, it was so much less
intensely illuminated, that the result was the same in tint as the
other side under the clear sharp light of the sky.

Many a person, looking down into the water from a bridge, sees nothing
whatever of the fish in the water below, because their backs are
exactly like the bottom of the stream. Suddenly one of the fish, by a
quick movement, turns its lighter under side over in such a way that
it is clearly illuminated from the sky. Immediately a flash as of
silver strikes the eye of the onlooker and makes him aware of the
presence of the fish which had previously been undetected. If rendered
thus suspicious, the observer will carefully examine the bottom of the
water, he may quite likely find dozens of fish which had previously
escaped his attention.

Nature is very versatile. So many of her apparently chance ventures
have proved successful that she has retained many devices by which her
children may be safe. One of these, which is doubtless often quite
effective and may serve to save an animal's life, is that of being
able to emit an odor so nauseating as to offend the enemy's sense of
smell, and doubtless remove the keen edge of his appetite. It is not
uncommon among the group of insects properly known as bugs to possess
an exceedingly unpleasant odor. Anyone who has handled a squash bug
will know exactly what I mean, and there are other members of the
group not so common as the squash bug, which, at least to the human
nose, are distinctly offensive. Some of the beetles also save
themselves by this device.

One of the most interesting developments of this peculiarity is found
in the case of the common skunk. This creature has in each groin a
gland capable of secreting a highly offensive fluid. Ordinarily this
liquid is kept safely within its sac, and for a long time none of it
may escape. When closely cornered, the skunk will turn its tail toward
the enemy and with a quiver and a flip of his tail it can guide the
openings of two little tubes that come out along the root of the tail
in such fashion as to eject the fluid in a fine and foul-smelling
stream against the animal from which the skunk would escape. Once
fairly hit by this fluid, I imagine most animals will drop the skunk.
A dog surely will, and will hate himself for having made the attempt
to capture anything which must be so ignominiously allowed to escape.
If ones clothing is well saturated with it, it is nearly useless to
hope to remove the odor. A dog will carry the smell for several weeks.
For a long time it will be so strong as to make him an unfit denizen
of the house. Even swimming in deep water does not remove it. After
two weeks, although he may seem to be practically free from the odor,
a light rain will bring it all out again and make him nearly as
offensive as before.

Not as prompt in its action, but in the end nearly as effective, is
the protective device which the toad sometimes uses to his distinct
advantage. May I be pardoned a personal account of this particular
feature. It was my good fortune to be for a short time a student in a
class taught by Edward Drinker Cope, one of the most brilliant of our
American biologists. Prof. Cope mentioned in class the fact that the
Batrachians (the group to which the toad belongs) have in many cases
the power to emit from their skin a fluid which is sufficiently
nauseous to deter an animal from eating the creature that secretes it.
Upon such authority as this, I had no hesitancy whatever in repeating
Cope's statement. One morning I had a class in the field studying the
ground ivy, whose dainty blue flowers were lifting themselves out of
the dewy grass. While we were thus engaged, a toad joined the circle.
He came out of his dewy retreat clean and fresh from his morning bath.
I took him in my hands, and made him the subject of an immediate
lesson. I showed to my pupils his eyes and his interesting method of
handling them, his tongue and its strange insertion; showed them how
to look into his mouth and look up his ears to his ear drums, and
pointed out many other interesting facts. Then I told them how Cope
had said that the toad had power to emit from its skin a fluid so
nauseous that many an animal hesitates to eat it. This is the first
peculiarity I had mentioned which I had not myself observed, and a
scientific qualm came over my conscience. Why had I never verified
this statement which I had so frequently repeated? On the impulse of
the moment, with the bright, clean skin of the creature fresh from the
dewy grass, making it less than usually repulsive, I ran my tongue up
its back only to find that it had no taste whatever. I was of course
surprised, but I was not foolish enough to deny, as the result of one
observation, the statement of a good scientist. The observation,
moreover, was one which I naturally did not care to repeat with any
frequency. Of one thing I was sure, toads do not always have an
unpleasant taste.

A year later I had a class down by the side of a neighboring pond. The
pool was not an attractive one, and I had picked from it a more than
commonly unappetizing looking toad, which proved to be a mother which
had not yet laid her eggs. As I held her in my hands and exhibited her
various points to my pupils, I told them of Prof. Cope's statement. I
also told them of my unsuccessful attempt the previous year to verify
the statement. I added, however, that I would not repeat this
experiment on this unappetizing specimen. Hereupon the toad not only
exuded, but squirted, from a gland over her left shoulder blade a
fluid, milky-like in appearance, and forming a jet as thin as a
needle, but ejected with force enough to strike my face, which was at
least fifteen inches away. I moistened my finger on my tongue, lifted
the fluid from my cheek, and tasted it. Cope was right. A toad can
exude a most nauseous fluid. Horsechestnuts extracted and distilled
might possibly provide something as bitter. Why did I not find this in
the preceding case? I have too few observations on which to base a
conclusion, but I have a suspicion as to the reason. In the case of
the toad which spurted the fluid in my face, we had a creature with
whose life were tied up the lives of her many offspring, to be
produced from the eggs she was so soon to lay. Under conditions like
these, nature is more than commonly careful of her children. Whether
this be the reason or not, toads do not always have an unpleasant
taste, but when they do it certainly is most unpleasant.

There remains to be considered the most effective plan yet mentioned
of escaping the enemy, and that is of really escaping. In all the
devices we have considered thus far the enemy is eluded. When the
creature lies quiet, or finds safety in its protective coloration, or
in its bad taste, or unpleasant odor, it still remains in the presence
of the enemy. A more progressive plan altogether is to escape the
enemy by flight. The great advantage of this plan lies in the fact
that the acquisition is valuable for every purpose. The creature then
can escape the enemy, can range widely for food or for a mate. This
gives it an enormous advantage in the struggle for life. The power to
fly, in insects, was doubtless originally gained in the attempt to
escape the enemy. Among many of the lower animals it is nearly the
only purpose that flying serves. Later on it enables the animal to
pass from one food locality to another. In a few creatures it plays an
effective part during the mating season. These last are probably both
derived powers, and the original function was that of escape from the
enemy. The grasshopper has grown its long legs to serve him for
safety, and through them it is helped along, moving about chiefly by
leaps when it wishes to go any material distance. It is only toward
the very end of its life that the grasshopper has wings, and then they
serve probably to aid in the search for a mate. Among the birds flight
began simply in sailing out of the trees, into which the creature,
still half lizard, had crept to escape its enemy. The earliest bird
known to us had comparatively insignificant wings. There was really
more support in its tail than in its wings, and this would distinctly
indicate that it glided more than it flew. It had claws also upon its
wings, and it was probably the case that this creature crept into the
trees, at least in its earliest forms, and sailed down in a manner not
unlike that employed to-day by the flying squirrel. From such simple
beginnings came the wonderful power of flight in the birds.

Among mammals the attempt to escape from the enemy has led to an
interesting development, which will be more fully explained in a later
section when we speak of the history of the horse. The early mammals
walked flat-footed, as we do on our feet and as the raccoon and the
bear do on theirs. Gradually, however, as their enemies became more
fierce and better able to injure the larger mammals, the latter gained
in power of flight, and this gain consisted first in rising from the
toes, lifting the heels completely off the ground. At the same time
the leg and foot were gradually lengthened. Doubtless in this way the
fleet animals, like the deer, the horse and the giraffe, first came by
their long legs. Constant elimination of the short-legged ones, by the
pursuing enemy, resulted in the selection of the long-limbed ones for
breeding purposes, and hence to the ultimate elongation of the legs of
the species.

The method of escape from the enemy involves cowardice. "He who fights
and runs away may live to fight another day," and so it may be the
part of wisdom in the weak creature to escape from his enemy by
flight. It is a far more estimable process, from our standpoint at
least, to stand against the onslaught of the enemy and beat him upon
his own ground. This end is secured in many animals by acquiring horns
or by lengthening certain of the teeth. The horn is a very ancient
instrument of defense. When the reptiles ruled the land horns were not
uncommon. They consisted in those days of hardened scales, which
lengthened and fastened themselves over a core of bone. Such an
old-fashioned instrument, sometimes made of newer materials, still
remains the defense of a number of animals. The rhinoceros has upon
his nose a lengthened projection, which is what might not improperly
be called hair glued into a cone. This enormous horn is a frightful
weapon, both of offense and defense, and, when backed by the terrible
weight of the body of the rhinoceros, it can do as deadly work as
almost any instrument of destruction known to animals below the grade
of man. But, after all, this is an old-fashioned method, and the
rhinoceros is a relic.

Among the carnivorous animals the teeth, which were developed first
chiefly for the tearing of flesh in its consumption, became effective
for their courageous owners. Because these tearing teeth are well
developed in the dog they have come to be known as canine teeth.
Usually where an animal can use its teeth effectively for offense or
defense, it is the canine teeth that are thus modified. The cat has
developed them better than the dog, and one of the cats of a bygone
geological period had canine teeth so magnificently enlarged and so
sharp at the back as to give this frightful creature the name of the
saber-toothed tiger. The long teeth in the upper jaws of the elephant,
commonly known as tusks, are not canine teeth. The elephant has
completely lost his canines. His tusks are his incisors, and they have
developed as have almost no other teeth in the mammals.

These are only a few of the numberless devices nature has evolved for
furthering the success of her children. There are so many others that
to many of us they form almost the chief point of interest in our
study of a new animal, or our closer observation of an old friend.



CHAPTER V

ADAPTATION FOR THE SPECIES


The strife, as we have described it thus far, is a purely selfish
struggle. Every point gained is a point favorable to the welfare of
the individual animal. But nature is uncommonly careless of the
individual unless the advantage gained is also of use to the species
as a whole. Very often the life of an animal ceases when provision has
been made for its young. The male garden spider may have a long and
dangerous courtship, in which the uncertain temper of his ladylove may
lead her to bite off four or five of his eight legs. But her
ingratitude is not yet complete. He may have barely accomplished his
desperate purpose of fertilizing her eggs at all hazards, when she
ends the process by eating him. The male bumblebee fertilizes the
female in the late summer and then dies. She does not lay her eggs
before the next season. So it happens that no bumblebee ever sees its
own father, and no father bumblebee ever sees his own children. In the
honey bee the male, which has been fortunate enough to fertilize the
queen, pays for his honor by death within the hour. Superfluous
bachelors, among the honey bees, when the bridal season has passed,
are driven from the hive to die of starvation.

An animal need not always be successful himself, but it is more
essential that he hand down his successful traits to those who come
after him. It is more important for the future generation that an
animal should have had it in him to do great things, though he himself
really have never done them, than that he should have learned to do
great things on a meager original endowment. Not what an animal
accomplishes is important to his children, but what he has it in him
to accomplish. Accordingly Nature is full of devices by which those
who have proved their original endowment by winning out in the
struggle shall hand on this endowment to a subsequent generation. In
other words, Nature is anxious that they may successfully mate. Here
we are again on distinctly debatable ground. Darwin himself believed
thoroughly in what he called sexual selection. It is the essence of
this idea that the males and females have grown unlike, more
technically have developed secondary sexual characters, through the
choice of the mating pair. It would usually be the more serious loss
if accident should come to the female, for she may carry fertilized
eggs for some time. Hence, if both sexes may not become attractive, it
is usually the male that develops fine colors, ornamental appendages
or a captivating voice.

An interesting reversal of this process has taken place in civilized
man. His more savage ancestor adorned himself more lavishly than he
permitted his mate to do. With the advance of civilization man has
undertaken to defend his own mate most valorously. The result is it is
safe for her to be beautiful. Under these circumstances, however, it
is more necessary to her welfare that her consort be vigorous rather
than that he be handsome. Hence in the human species beauty has become
the prerogative of the woman, and this is increasingly the case the
higher the civilization. Whether woman suffrage and self-support will
reverse this process remains to be seen. There are indications that
point that way.

There are many biologists who are at present expressing serious doubt
as to the validity of sexual selection. As in the previous cases of
protective coloration, I believe it will be wise for us to retain,
even though with an interrogation point behind it, the idea of sexual
selection until such time as those who object to it have furnished us
with another theory which will more nearly account for the observed
facts. While entirely conscious of the possibility that there is a
weak spot in the theory, we will still tentatively hold to sexual
selection. The fact that beauty in women is so intensely attractive
to man, and that vigor and manliness in man are so attractive to
women, leads us to infer that among the lower animals, although of
course in a vastly less degree, vigor and beauty are also attractive.
The weakest point of the position lies in the fact that it probably
presupposes a higher degree of capacity for appreciation on the part
of lower animals than they possess. Those who deny the truth of the
theory laugh at the idea that a butterfly can see clearly enough and
care enough for what it sees to notice whether its mate has wings of
one type or of another. The size, number and position of the spots on
the wings of many butterflies are so nearly constant that they cannot
of themselves have been entirely determined by the choice of the
insect. Yet this may not preclude the possibility of the fact that,
while the spots were produced through some other agency, certain types
of them were selected by sexual preference.

If attractive coloration is effective anywhere in the animal world, it
will possibly be found among the insects, but it is especially likely
to be found among the birds. Very many field workers in these groups
feel quite sure of the value of attractiveness. When butterflies chase
each other up and down, circling and doubling, following each other
for long distances, it would certainly seem as if they were pleased
with each other's appearance. Some naturalists, especially those who
have worked chiefly in the laboratory, insist that it is the odor, not
the color of these insects, which is attractive, and some experiments
which have been made would seem to point in this direction. But the
creatures experimented upon most carefully were night-flying moths,
and it is quite possible that the sense of sight in the night-flying
moths has lost its vigor.

The great difficulty in understanding sexual attraction in insects, as
based upon beauty, lies in the undoubtedly lower development of their
nervous activity; in other words, in the apparent absence of anything
worth calling mind. I think no one imagines that a butterfly, looking
upon two other butterflies who are competing for her affections,
deliberates between them and determines to admit to the circle of her
friendship the more brilliantly colored male. Moths are so
irresistibly attracted to a light as to fly into it without apparent
power to withstand its influence. They repeat the flight again and
again until they are destroyed. If they react so vigorously to the
stimulus of the light, it seems not impossible that they may also act
vigorously to the stimulus of color pattern, and that the male most
beautifully colored, according to the nervous ideal of the female,
should win her unconscious regard. At least it is certain that, in
very many of the butterflies and moths, the attractive coloration is
chiefly displayed when they are moving actively about; and when they
alight and their enemies can the more easily capture them, they
conceal their brilliant colorings. Most butterflies are very brilliant
on the upper surface of the wings and very much duller on the under
surface. Hence in flight they show their colorings exquisitely, but
when they alight, and are thus more likely to be captured, they fold
the brilliant surfaces together in an upright position. In this way
not only is the dull side of the wings placed outward, but the wings
themselves are placed edgewise to the sky, and it is from this
direction that their enemies, the birds, are most likely to see them.
Once upon the wing these creatures display their beauty with much
greater safety because they can escape the birds very readily by use
of their exceedingly jerky flight. The butterfly's motion is as
irregular as any we have except the bat's. This eccentricity is one
great element in their safety, and makes it less dangerous for them to
display their attractive colorations.

One very large group of the night-flying moths have been named the
"underwings," because of the fact that their hind wings are very much
more brilliant than the front, and in lighting they fold the dull pair
back over the bright, completely concealing them. These creatures are
in the habit of resting in the daytime against walls, or stones, or
the bark of trees. The similarity in color between their front wings,
which alone show while sitting, and the background on which they rest,
is most remarkable. One may pass them again and again, although they
are of considerable size, and not notice them at all. Once let them
display their hind wings and the brilliancy of their color always
attracts immediate attention.

It is among birds, however, that brilliant coloration serves its most
effective purpose. The birds are alert, exceedingly quick of sight,
and are much more discriminating than insects in almost every respect.
It is not so impossible that these creatures might even voluntarily
prefer a distinctly more brilliant mate, though the voluntary
character of the process is not essential to its success. Men
certainly are constantly attracted to women for whose charm it would
puzzle them to account. If this is true with regard to men, it is
certainly probable that birds would be largely influenced by phases of
attractiveness, of which they were observant, but unconscious.

Certain it is that in many birds the males are far more beautiful than
the females. Perhaps the commonest illustration, and, at the same
time, one of the best is found in the so-called red-wing or swamp
blackbird. The male of this creature is a brilliant black, excepting
that upon the angle of the wing, spoken of roughly as his shoulder,
though in reality it is equivalent to our wrist, there appears a
splendid orange patch with a border of lemon yellow. When he folds his
wing he pushes this colored angle of the wing so deftly under the
feathers of his shoulder as almost to conceal it. When in flight the
bird is exceedingly conspicuous, showing, with every bend and twist of
his body, his gorgeous epaulets. Meanwhile, the female is likely to
pass unnoticed. She is dull in color and streaked like the grass among
which she lives. During the mating season the male hovers about her,
swaying from side to side in such a way as certainly to make it appear
as if he realized his good points and was bringing them to bear as
effectively as he knew how. After his mate has nested and is rearing
her young, it would appear that the male uses his brilliancy to lure
the observing enemy away from the nest containing his wife and
children.

Another illustration of the remarkable superiority of the male over
the female, in many parts of the bird world, is seen in the case of
the common barnyard fowl. The rooster is so much more gorgeous than
the hen that anyone reasonably acquainted with these birds cannot have
failed to notice the fact. In some of our modern varieties we have by
breeding colored them nearly alike. The original chicken is colored
much like the common Leghorns. Shades of red and yellow decorate his
neck and back, while the flight feathers of his wings and of his tail
and the sickle feathers which ornament the rear of his back and hang
over his tail are lustrous dark green. The hen meanwhile is very much
less brilliant in her contrasts. I shall speak more fully of this in
discussing polygamy.

The attraction of beauty is not the only lure by which a creature may
win its mate. Sound may captivate as effectively as beauty. This is
true of insects as well as of birds. Certain insects at least advise
their mates of their presence by means of a sound which they emit.
This is particularly noticeable among the group of straight-winged
insects to which the grasshopper, katydid and cricket belong. The
grasshopper has a ridge on the angle of his wing and a roughness on
the side of his leg. When these two are rubbed together the result is
sometimes a fiddling, sometimes a snapping or cracking sound,
differing in different grasshoppers. I doubt not these sounds are
pleasing to the female of the species, for they are always made by the
male. The katydid, instead of fiddling in this way, has a sort of drum
on the angle of his one wing, which he can rub over a tooth in the
corresponding angle of his other wing, thus producing the familiar
"katydid" sound. I have never succeeded in making a dead grasshopper
fiddle, but I have long known how to make a dead katydid say "ka."
Quite recently I have added to my accomplishment in this respect and
can make it say "katy." The "did" part of the song still lies beyond
my power. The crickets produce their sharp notes in much the same
fashion as the katydids.

One observer of the chirping of the cricket says that the pitch of the
song varies with the temperature. He has even worked out a formula by
which one can tell the pitch of the chirp, if he knows the
temperature, or, knowing the temperature, can determine the pitch. Of
course this is too mechanical; yet it indicates that there must be
considerable relation between the two; the warmer the cricket the
happier he is.

It is the males among insects that chirp their love songs. The females
never answer them. There is a peculiar notion that the female katydid,
when thus accused of some offense, replies "katy didn't." The truth of
the matter is that no female katydid ever replied to the accusations
of her lover, if accusation it be. She is absolutely dumb, not having
the drum upon her wings with which to reply. She is provided with ears
wherewith to hear, and, strange to say, she keeps them on her elbow,
as does also the cricket, while the grasshopper has his ears upon the
side of his body.

Everyone who lives in the country, or goes into the country in the
summertime, is sure to know the humming of the so-called locust. It is
an unfortunate fact that the word locust may have several meanings. It
is properly applied to one group of the grasshoppers. The creature
most commonly called a locust is a cicada, or harvest fly. When the
weather gets quite warm the cicada starts his love song. He has two
long flaps to his vest, and under each flap he has a vibrating drum
head. This is set shivering by a muscle on its under side. The female
cicada again is silent.

It is among birds that the love song reaches its finest development.
It may consist simply of a little chirp as in the chippy. It may
consist of two notes of a different pitch repeated steadily, as in the
tufted titmouse. It may attain considerable variation, as in the
robin. But in the choir of our best singers, like the catbird,
thrasher, and mocking bird, there is unending variation of notes. It
seems almost impossible to doubt the charming quality of this voice
upon the mate. It certainly is chiefly confined to the mating season,
and is indulged in almost entirely by the males. This does not mean
that a male does not sing excepting when he wishes to charm his mate.
But the time when he is in his most exquisite feather and most
charming mood is the time when he sings most sweetly, and this is the
time when he is taking to himself a mate. The love joy may so
overcrowd his life that he sings much and often, but the increase in
its amount and character during the mating season seems to proclaim
its purpose beyond a doubt.

In addition to the allurements above described there are certain
peculiar behaviors of the animal during the mating season which are
intensely interesting. Sometimes they consist simply of a wild
delirium of joy, which overpowers the animal completely and makes him
do wonderful things. Birds will fly with impetuous leaps in the air,
mount higher and higher, singing wildly, only to turn suddenly at the
top of the flight and drop promptly to the ground. I have seen such
ecstatic flights in the oven bird and in our rollicking gold finch. I
have seen a catbird on his way to a tree turn three somersaults, much
like those performed by a tumbler pigeon, after which he alighted upon
the bough. None of these acts seemed deliberately performed in front
of the females, but I have seen three or four killdeer parading in
most stately and precise manner, spreading their wings and fluffing
their feathers, performing a sublimated cup-and-cake walk amid a
circle of attracted females.

Even our little English sparrow, as I have previously mentioned,
fluffs himself up and spreads his wings and prances around in front of
his presumably adoring ladylove. But the weirdest performance of this
sort I have ever seen is that shown by the male ostrich. When he
becomes excited, swaying his body from side to side, he sinks slowly
upon his knees, until his body touches the ground, his wings spread on
either side and the feathers fluffed up so as to show every exquisite
plume in all its splendid beauty. The long neck is laid back until the
head, which is doubled sharply forward, is pressed almost against the
back, and in this strange position he sways from side to side,
apparently utterly oblivious, for a time, of everything. After about a
minute of this performance, he seems slowly to come to himself and
rise again to his feet. Now he is particularly likely to make vicious
attack upon anything within reach.

It is not only necessary that the animal should be able to attract a
mate. There may be more than one claimant for the damsel's affection.
In many animals we see provisions whereby the male may effectively
deal with his rivals. This is especially likely to be the case if the
animal be a polygamist. In every species there are produced about as
many males as females. If the polygamous habit leads one male to
gather about him a group of females, with whom he mates, it is evident
that he is displacing an equal number of rivals, and they are not
willingly displaced. Accordingly we find that polygamy is usually
accompanied by a belligerent disposition on the part of the males. In
our ordinary barnyard fowl this trait is very evident. The rooster not
only domineers over the hens, not only struts about among them in
stately fashion and gives vent to his feelings by his sonorous voice,
he must also drive away from the neighborhood any rivals for the
affections of his wives. Hence the rooster attacks upon sight the
neighboring rooster, and battles with him to his entire discomfiture
and sometimes to the death.

Among the members of the deer family this particular phase of the
relation between the sexes has produced in the males, and only very
rarely in the females, the magnificent branching horns. These are
intended not so much as a protection against the enemy as for an
offensive weapon in the battle for the mates.

Beautiful and stately as are these magnificent horns, they last only
for a part of the year. We begin to understand their meaning. When the
wolf is hungriest, toward the close of the bitter winter, the deer is
without horns. When the time for mating comes, the deer within a few
weeks grows his horns, which at first are covered with a plushlike
coating, known as velvet. After a while this dries and he rubs his
horns against the trees until they are clean and smooth. Now he is
ready for the battle royal.

In the case of the fur seals polygamy has carried its specialization
of the males to a remarkable extent. The bull seals are several times
as large as the cows, and are provided with terrific canine teeth.
With these they battle with a violence that very often results in the
death of one of the combatants. A successful bull seal who has
gathered about him a cluster of seal cows is seamed and scarred with
the marks of his annual combats.

One more type of adaptation can be profitably considered. Animals have
developed many devices which serve for the protection of their young.
The wonderful silk spun by the spider was evidently primarily intended
to serve as a covering for the eggs. Probably all of our spiders agree
in using the silk for this purpose. Many of them employ it for
practically no other, though there are half a dozen different uses to
which different spiders may put their silk. Under these conditions we
have a right to infer that silk was primarily developed as a coating
for the eggs. In the case of some of our spiders a little fluffy mass
of silk covers the egg, while a firmly woven sheet of silk covers both
egg mass and fluff, holding it flat against a wall or the trunk of a
tree. In some of the higher spiders, notably our bank spiders, the
silken covering becomes an effective cocoon, spherical in shape, with
a little opening at the top like the neck of a small bottle. The egg
cocoon is woven in a mass of tangled silk between the branches of some
tough weed which will be sure to outlast the winter. Into the egg
cocoon the spider may place one thousand or more eggs. Having thus
provided her children with a snug winter home, the spider dies. When
spring comes with the warm rays of the sun, the eggs hatch and the
cocoon becomes a creeping mass of minute spiders. At the time these
spiders appear there is nothing for them to eat. The obvious way out
of this difficulty is taken. At once there begins a progressive party.
Spider fights with spider, and the prize in each conflict is the body
of the victim, which is promptly eaten. The winners in the first round
pair off again, and a little later, as hunger drives them, another set
of combats comes on, resulting in another halving of the number of
spiders in the cocoon. This process continues until not more than
one-tenth of the original number of spiders remains. By this time they
have gained sufficient strength of leg and jaw, and sufficient
dexterity in the use of both, to make it safe for them to venture out
and try their fortunes among the accidents of a strenuous world. There
can be little doubt after this long process has worked its final
results which tenth remains. Chance plays but small part in this
game. It is the fittest that survive. When this procedure goes on
generation after generation, the result must necessarily be that the
spiders grow fitter and fitter for their work. This method is hard on
the little spider, but it makes good spiders.

Most insects die before their eggs hatch; accordingly they can pay no
attention to their own children. Whatever arrangements are provided
for the safety and strength of these offspring must be provided before
they appear. About the only care the majority of insects take in this
direction is to see that the eggs are placed where the young shall
find food as soon as they emerge. Insects' eggs are very small, and as
a consequence the creatures which emerge from them are likewise
exceedingly minute. As a result they cannot be expected to hunt far
for their food. Different insects use different devices by which to
overcome this difficulty. The katydid, for instance, must die with the
approach of fall. Her children will not appear until the following
year. Her food consists of leaves, but to lay the eggs in such a
situation would be a fatal process, because the leaf will drop off
before the eggs hatch. Accordingly, the katydid lays its shield-shaped
eggs in a double row near the end of a young twig. Next year when the
weather is sufficiently warm to hatch katydids, it is also warm enough
to force the buds on the end of the twigs. When the katydids arrive
their jaws are young and tender, but so are the leaves upon which they
are born. Hence there is little difficulty on the part of the young
katydids in finding an abundance of food. By the time the leaves have
grown tougher, the katydid's jaws are stronger, and the leaves will
still serve as food.

Everyone who is at all familiar with country life and gardening is
familiar with what is called the potato or tomato worm. It is a long,
green, smooth, caterpillar, as long and as fat as your finger and
provided with a horn upon his tail. The gardener may not know that
after a while this creature will burrow into the ground, and there
change into an oblong brown mass with a sort of a pitcher handle at
one side. Next year this pupa will split down the back, and from out
of the brown case will come a hawk-moth, which soon will fly with
rapidly quivering wings and feast upon the nectar of our moon flowers
or on that of the "Jimson" weed. Those who have cleaned these pests
from the potato or tomato vines will often have noticed one of them
covered with what look almost like grains of rice. This appearance
reveals an interesting story. Some time earlier an insect that looked
very much like a dainty wasp with a rather long sting in its tail
hovered over the caterpillar. This is the ichneumon fly. Eventually
lighting upon the caterpillar's back, it punctured the skin with its
sting, and deposited eggs within the caterpillar's body. These eggs
soon hatched and the little grubs worked their way through the body of
its host. The infested victim feeds upon leaves and fills itself with
rich food. These parasites eat the food, and, try as it may, the
caterpillar does not succeed in getting fat. After the grubs have
gotten their full growth, each of them eats its way through a little
hole to the outside of the caterpillar's body. Here it spins around
itself a little white case, and looks like a rice grain. As the
caterpillar moves about, these seeming rice grains are rubbed off and
fall to the ground. Next year there will come up new ichneumon flies
to sting fresh caterpillars and repeat the entire process.

Another remarkable provision for the young on the part of insects is
seen in the behavior of the big sphex wasp, known as the cicada
killer. The cicada, it will be remembered, is what is commonly called
a locust. The cicada killer is a magnificent big wasp, whose body is
nearly an inch long, banded with black and yellow, while the wings are
colored a smoky brown. This muscular wasp digs a long tunnel eight or
ten inches deep, which ends in a slightly larger room. Having provided
the location, he now sallies forth in search of the cicada. The heavy
song of the male probably serves as a guide to the wasp in case of
scarcity of cicadas, but the killer has apparently little difficulty
in finding his prey. The wasp pounces upon the insect, and in spite of
its strength and the thrashing of its vigorous wings punctures it with
his sting again and again. The poison of the sting entering into the
nerve centers gradually paralyzes, but usually does not kill, the
cicada. Now the killer carries its prey home, pushes it to the bottom
of the tunnel and deposits upon it a single egg. The wasp closes up
the hole and leaves the place. When the egg hatches and the grub of
the wasp emerges, it finds a big cicada just at hand, upon which it
feeds. By the time the cicada is completely devoured, the wasp grub
has obtained its full growth. After a short period of development a
new sphex wasp is ready to work its way out of the tunnel, find a
mate, dig a hole, and safely provide for its own children.

Still more remarkable adaptations for the care of the young appear
among the birds. Here the eggs are not to be deserted, but are to be
cared for until the young appear. These again must have attention
until such time as they are quite able to take care of themselves. The
birds are warm-blooded animals, and even their young, while they are
developing in the egg, are warm-blooded. Consequently the temperature
of the egg must be maintained evenly and uniformly, or there will be
no development.

The fish may drop its eggs carelessly upon the bottom of the stream. A
frog may deposit them in a mass of jelly and leave them forever. A
turtle may bury its eggs in a sand bank and abandon them to their
fate. The warm blood of the young bird demands more attention than
this. Accordingly, the parent bird has learned to make for itself some
sort of nest, in which the young may be kept properly warm until they
are developed. The ancestral bird, who was to be the progenitor of the
entire bird class, must have had some very simple method of providing
a place in which its eggs might be hatched. As the descendants of this
original bird have passed into new situations, the various lines have
taken upon themselves different shapes until we have the multiform
birds of to-day. The habits of the birds have also varied. Each has
adapted itself to the situation in which it found itself, and no
adaptation has been more varied and effective than the adjustment of
the nesting site. Nests are found upon the ground, in the bushes, on
the lower limbs, in the crotches of the trees, in the trunks of the
trees, upon their very summits, and on the tops of inaccessible crags.
To every sort of situation some bird has been enabled to adapt itself.
This has made it possible for very many more birds to thrive than
could have found a place in the world, had they all lived upon the
same plan.

In the case of the bank swallow his nest may be a very simple
contrivance, consisting only of a tunnel running back into a bank, and
widening at the back. Some material that will soften the bed upon
which eggs are to be laid must be placed in this cavity. The whole
home is a very simple and crude affair. But little better is the
arrangement which the woodpecker calls a home. This has been cut into
the dry wood of a defective tree. No woodpecker can make his home in
absolutely solid sapwood. Hence the first labor of the woodpecker must
consist in finding a place in which it can dig. If there is an old
stump of a limb sticking up, the problem is readily solved. Such wood
has no sap in it, and is brittle enough to be easily dug out. But, if
there be no such stub, the woodpecker will find a suitable place in
most trees. At some time or other almost every tree loses a big limb.
When such accident occurs there will always be in the old trunk a
region through which sap once went to this limb. This region, deprived
of its function, goes completely dry, like the heartwood of the tree,
and it is into such material as this that the woodpecker succeeds in
drilling his well-protected home.

As birds rise higher in the scale the nest-building becomes a more
complicated affair, and after a while we find a well-woven substantial
nest, through which even the air will not chill the eggs enough to
prevent their hatching, while the warmth is supplied by the mother's
body. It is often a matter of surprise to many people that a bird
should contrive to build a nest so exquisitely circular. The trick,
after all, is not quite so difficult as it looks. The robin gathers up
a few sticks and places them as the beginning of the platform. More
and more are brought and woven into each other, making a framework
altogether too big for the nest. Then mud is brought and plastered
inside of this. With the plastering of this mud the careful
circularity of the work begins. Every time a little material has been
added the robin sits down in the nest and revolves her body, in this
way shaping the interior much as the potter shapes a pot. In the case
of the artisan, it is the pot that revolves. In the case of the robin,
the bird itself revolves. The effect is the same in both cases--a
circular vessel is produced. A little lining added to the interior of
the nest softens it for the reception of the eggs. In this exquisite
home the robin lays her eggs, and sits upon them until they are
developed enough to hatch, and then feeds the young until they are old
enough to feed themselves.

Far more remarkable than any of the devices thus far described are the
wonderful developments which have come in the class of animals known
as the mammals. Here the most wonderful protection is made for the
care and feeding of the young. But this is to be the subject of a
separate chapter.

As long as we thought of each sort of animal as being a separate
species shaped in the beginning by the hands of the Creator, each of
these devices seemed to us a new manifestation of the Divine
Providence, whose fertile planning had conceived so many methods of
providing for his children. Unconsciously we thought of God acting as
man acted. Each animal seemed a purely separate invention purposely
designed for an especial place. Now we understand the plan in creation
better, and see that each animal has come from another not quite like
itself, some distance back, and this from still another. Our
admiration for these devices as they arise through evolution is no
less, but takes on another form.



CHAPTER VI

LIFE IN THE PAST


Anyone who earnestly studies plants and animals as they exist in the
world to-day cannot help wondering how the earth began and where it
got its life. This is the true end and aim of geological study. The
history of man seems to run back into a far distant and gloomy past.
Except for the poetical account in Genesis and the traditions of
various peoples throughout the world, real history fades away into an
earlier time of which there are no written records. When the delvers
in the Mesopotamian plain talk to us of kingdoms running back through
seven or eight or nine thousand years, we seem to be getting back to
the beginnings of things. But seven or eight or nine thousand years
are as nothing in comparison with the age of the earth, which runs
back into a past so limitless that no man can safely assign any set
figure to it. In a recent paper, Dr. Walcott, of the Smithsonian
Institution, says that the antiquity of the earth must be measured not
in millions, for they are too short, nor hundreds of millions, for
this carries us too far, but must surely be measured in tens of
millions of years.

When we attempt to study the past we find its various epochs unequally
clear to us. In human history only quite modern times are absolutely
clear. The history of the Middle Ages is distinct enough for us to
build for ourselves a picture of the time with reasonable hope of
gaining a correct view of the state of affairs. Back of this comes the
long stretch of the Dark Ages, in which here and there we have bright
spots, but it will perhaps long be impossible to portray clearly the
life of the people. Getting back to the Romans, things once more
become reasonably plain, as is true also in the case of Greek history.
Back of this stretches the Egyptian with fair precision, and, older
than it, the Babylonian and Chaldean. But these past three have not
left nearly so definite an account for us as did the later
civilizations of Greece and Rome.

When we try to go back of these we must change our method of study
entirely. Writing is absent, and all we know of earlier men must be
inferred from a few pictures that were daubed on the rocks or carved
in ivory or bone, from tools made of stone or bone, from a few metal
or stone ornaments, or from the bones of the men themselves. Even so,
the history fades out without telling us its own beginnings. It is
quite as impossible for history to write its origins as it is for man,
from his own knowledge, to describe his birth.

What is true of the human story is quite as true of that of the earth.
Recent steps are very plain. We may read them with considerable
confidence. As we go deeper into the rocks and find older fossils, the
evidence becomes less certain. The animals differed enough from those
of to-day for us to be less sure what they were like. As we keep on
moving backward through time, and downward through the rocks, we find,
after a while, strata in which there are evidences of life that
existed long ago, but in which these traces are so altered that it is
impossible to tell what sort of living things existed; we learn only
that they were alive. Going back still further, these fade out. There
is no knowing when the earth began; there is no knowing when life
began upon the earth. It is not meant that men have not wondered, even
reckoned carefully, as to how long ago each of these events occurred.
Many speculations have proved entirely useless, a few remain as yet
neither confirmed nor disproved, and of such we shall speak.

For the last hundred years the theory of the earth's origin suggested
by the Marquis Pierre Simon De La Place, of France, near the end of
the eighteenth century, has held almost undisputed sway among men who
were willing to consider the question as open to human solution. This
theory is known as La Place's Nebular Hypothesis. When men began to
study the heavenly bodies with the newly invented telescope, new ideas
naturally sprang up. Among the objects which the glass disclosed were
the nebulæ, which are great clouds of fire mist, glowing masses of
gas. They are scarcely visible to the naked eye, but are among the
most interesting objects in the heavens when seen through a telescope.
The other suggestive heavenly body was our sister planet, Saturn.
Besides having a full complement of moons, Saturn has around it, as
distant as we would expect moons to be, three great rings. These look
very much as if one's hat, with an enormously wide brim, should have
the connection between the rim and the hat broken out completely, but
the rim should still float around the hat without touching it and
should steadily revolve as it stood there. The rings of Saturn are not
solid like the suggested hat rim. They are evidently made up of a
great number of very small particles, each moving around the center of
Saturn. But the great cloud of them is spread out flat. At the
distance which Saturn is from the earth they look as if they made a
solid sheet. Furthermore, they do not form, as it were, one continuous
hat rim, but it is as if the rim were broken into three circular
sections, each bigger than the one inside it and separated from the
next by an area nearly as wide as the ring itself.

With such material in the heavens to guide him, La Place suggested
that the sun had once been an enormous fire mist scattered over an
area billions of miles in diameter. This gaseous material, by the
attraction of its particles for each other, began to condense and
contract. When the plug is pulled from a washbasin the particles of
water, in moving toward the center, in order to get out of the basin,
invariably set up a rotary motion. As the particles of this diffused
nebula began to gather together they, too, gave to the mass a rotary
movement. This grew more and more rapid, with greater contraction,
until the particles on the outer edge of the rotating mass had just so
much speed that the least bit more would make them tend to fly off as
mud would fly from a revolving wheel. When this point was reached
there was a balance of forces which made the outermost portion remain
as a ring while the rest contracted away from it, leaving it behind.

It was La Place's idea that this process had repeated itself, and ring
after ring had been left behind. Finally the sun condensed and grew
into a ball, occupying the center of the system. At varying distances
from it were to be found either rings or planets which had been formed
out of such rings. For La Place suggested that in a ring like this
the material could not be quite evenly distributed. While every
particle in the ring kept revolving around the sun, those in front of
the densest part were slowly held back by the attraction of the
thicker portion, while those behind it in rotation had their speed
hastened until finally all the material in the ring had collected at
one spot and a new planet was born. La Place believed that these
planets formed their moons in exactly the same way, and that Saturn
was simply a planet not all of whose moons had yet been formed. He
believed that this happy accident served to tell us how the universe
had been created.

Of course, so detailed a theory concerning anything of which we know
so little has always had much ridicule thrown upon it, and yet no
truly competing theory has been proposed until very recent times.

Within a few years a Planetesimal Theory has been announced, and is
gaining considerable prominence, although it is too early yet to say
whether it will supersede La Place's idea. In this theory, also, the
suggestion comes from the heavenly bodies. With the increasing study
of the nebulæ, many forms of these interesting bodies have been
discovered. A very common type consists of a great coherent central
mass, with two or more arms extending from opposite sides in the form
of a spiral. This is as if gaseous revolving nebulæ had come into
comparatively close proximity to a passing body. The visitor, by its
attraction, drew from the nebula a wisp of gas. The revolving motion
of the nebula gave to the attracted arm the spiral form.

These twisted arms are not equally dense throughout, but have
thickened knots here and there in their course. The Planetesimal
Theory suggests that these thickened knots are embryo planets and the
central portion of the nebulæ an embryo sun. After all the material in
such a body has condensed either around the knots or about the central
mass a new solar system will be complete. As before stated, neither of
these theories can be said to be demonstrated. Each of them has points
in its favor and each has its difficulties. It is pleasant to know
what men have clearly thought concerning such questions, but for a man
not a trained geologist neither will carry much conviction. He will
still rest with his own early conclusion that whichever shall prove to
be true, for him his old formula is still valid, "in the beginning God
made the heavens and the earth." He will no longer think of God as
having shaped the balls with his own hand and thrown them into space;
he will no longer dream that it all occurred within a week not more
than six thousand years ago; but still to him will come the reverent
conviction that, whatever the plan by which it was accomplished, it
was still God's plan and God carried it out.

Now that we have tried to stretch our imagination back to the origin
of our globe, the question not unnaturally comes to our mind, how long
ago did all this happen? Is there any possible means of telling when
the history of the earth began? All such attempts lead either to
indefinite or to uncertain conclusions. Each man who essays the
problem approaches it from a different side and ends with a different
result. But no matter what the method of approach, all are agreed on
at least one point, the enormous length of time, as counted in years,
through which the earth has lasted.

One great mathematician worked on the basis of the rate of the present
cooling of the earth. Counting backward to the time when the earth's
surface must have been hotter, according to La Place's idea, he
decided that our globe has been cool enough for the existence of life
upon it for a period of somewhere in the neighborhood of one hundred
million years. Those who try to study the rate at which mud is being
deposited in our bays and at the mouth of our rivers, and who hence
try to deduce how long it has taken to produce the thickness of all
the stratified rock we know, arrive at a figure larger, rather than
smaller, than that mentioned above. The same is true of those who try
to count the age of the earth by the rate at which the present rivers
are carrying away their river basins, and hence who calculate how long
it has taken the rivers of the globe to wash away all the rocks which
it is quite clear have been carried out. Still others have attempted
to solve the problem by seeing how much salt the rivers are carrying
into the sea, and consequently how long it must have taken the sea to
become as salt as it is. A very late attempt has been based on the
alteration in the minerals that show radio-activity. Conservative
estimates, based on all of these, would give us a figure on which we
must not count with any exactness, but which will serve at least to
mark the present trend of opinion. We may put this figure at one
hundred millions of years.

The following table gives us the names of the periods into which the
geologist has divided the past history of the earth. The first column
gives a simple name, which, in each case, is a translation of the
technical name the geologist gives to the era. This technical name is
also given in parenthesis. The second column shows the number of years
ago at which this period may be placed, while the third column gives a
series of names most of which are in use in geology and which are
intended to indicate the stage of advancement of the higher animals in
that particular period. Some of these names are perhaps giving way to
later terms, but all of them will be understood by any geologist.
Most of them will serve to keep very clearly before the mind of the
ungeological the period which he is studying. Like all such tables,
this must be read from the bottom up. This arrangement is used because
the oldest rocks in the series are naturally at the bottom and the
newest rocks are on the top, though occasionally a region is
sufficiently upset partly to reverse the order.

                      TABLE OF GEOLOGICAL TIMES

    ------------+------------------------+---------------------------
                |  MILLIONS OF YEARS AGO |  STAGES OF ANIMAL
      ERAS      |   (VERY UNCERTAIN)     |    DEVELOPMENT
    ------------+------------------------+---------------------------
                |                        |  Age of Man
    Recent Life |                        |   (Quaternary)
     (Cenozoic) |      0 to 5            |  Age of Mammals
                |                        |    (Tertiary)
    ------------+------------------------+---------------------------
    Middle Life |                        |
     (Mesozoic) |      5 to 10           |  Age of Reptiles
    ------------+------------------------+---------------------------
                |                        |  Age of Amphibians
                |                        |    (Carboniferous)
    Ancient Life|                        |  Age of Fishes
     (Palæozoic)|     10 to 25           |    (Devonian)
                |                        |  Age of Invertebrates
                |                        |    (Silurian and Cambrian)
    ------------+------------------------+---------------------------
    Dawn Life   |                        |  Earliest Animals and
     (Eozoic)   |     25 to 50           |   Plants
    ------------+------------------------+---------------------------

Having seen what the scientist supposes to be the method of formation
of the earth itself, it will be interesting next to consider what the
biologist surmises as to the origin of the life upon the earth. Here
again two explanations hold. The one, and distinctly the older of the
two, says that at some time in the far distant past, under conditions
which are rarely if ever duplicated, out of the lifeless material of
the globe were produced simple and low forms of life. These could not
properly be called either animal or plant, but partook somewhat of the
nature of both. Of this there is at present no evidence whatever. The
only reason we have for suggesting it is that, if we understand the
past conditions on the earth, there was a time when life was
impossible. Now we find life. Hence it must have arisen. This of
itself, of course, furnishes no proof, but leads us to try to imagine
how the transition might have come about. Every scientist who believes
in this form of origin holds that if the exact conditions are repeated
the result will occur once more. He may believe that no such
repetition is possible, but he is confident that, if it could be, life
would arise again from lifeless matter.

This process of life arising from matter that is not alive is known as
Spontaneous Generation. Two hundred years ago it was supposed to occur
frequently. It was common belief that the beautiful pickerel weed
which borders our Northern lakes, after freezing, went into a sort of
protoplasmic slime out of which pickerel were produced. The eelgrass
of the river was supposed to yield eels in a similar fashion. The dead
bodies of animals were supposed to turn into maggots. Such crude ideas
of spontaneous generation are no longer possible. The whole science of
bacteriology absolutely presupposes the impossibility of spontaneous
generation in the flasks and test tubes of the laboratory. One or two
men of otherwise good standing in science still maintain that they are
getting new life in their own test tubes, but they fail utterly to
persuade the scientific world. I think it is a fair statement of the
position of science to-day to say that there is no evidence whatever
of spontaneous generation, excepting the presence of life upon the
globe.

Not all has been said, however, on this question. The chemist is
learning in the laboratory to produce many substances which, until
very recent times, were produced only in the bodies of animals or
plants. Dye-stuffs were originally gotten almost entirely from animal
or plant material. At present the great majority of them are made in
the laboratory, and in not a few cases they not only imitate the color
of the older material, but actually have identically the same
composition and constitution. The laboratory-made material is exactly
like that made by the animals or the plants.

The same is true with regard to a large number of the fruit flavors.
These are due to the presence of ethereal oils in the plant, and their
exact counterparts can now be produced in the laboratory, and can
serve every purpose of the fruit flavor itself. Alcohol has been
produced artificially, and alcohols, which nature never dreamed of
making, so far as we can tell, but which are made on her plan, are
manufactured by the chemist. Last of all, sugar has recently been
built up by the chemist, though the method at present is so expensive
that it cannot possibly compete with the production of the commodity
from the cane and the beet. As in the case of alcohol, all the sugars
that nature makes can now be made artificially, and others of the same
general plan which she seems not to have as yet devised can be
produced within the laboratory.

Attempts have been made to manufacture proteids, but these have as yet
eluded the efforts of the chemist. He is beginning, however, to come
nearer understanding their composition, and when he once clearly
comprehends that he may be able to reproduce them.

One of the German chemists is convinced that the nuclein in the
nucleus of the cell is not a very complicated compound. Under such
conditions it is not a matter of surprise that the physiological
chemist should be constantly dreaming that he may at some time produce
living matter in the laboratory. To the ordinary mind it scarcely
seems possible. We are so entirely sure that life is not amenable to
physics or chemistry that we can hardly conceive of the possibility of
its originating out of matter in the test tube. If it does so come,
and when it does so come, this will not prove that life is a less
noble and less wonderful thing than we thought. It will only prove
that chemistry and physics are more noble and more wonderful than we
dreamed.

There is another way of approaching this life problem, though it seems
to be rather a begging of the question than a solution of it. Of
recent years it has been discovered that even the very low
temperatures obtained by evaporating liquid air, say three hundred
degrees below zero, Fahrenheit, do not kill seeds or spores of mold.
The space between the planets is undoubtedly extremely cold. We have
always supposed it to be entirely too cold for life to exist in it.
But we laid little stress on the fact because we had no thought of any
possible life existing there. But the discovery that seeds and spores
can live uninjured through extreme cold has led to an interesting
suggestion. This is that when the earth became adapted to the presence
of life it was infected by germs transported on meteors from some
other system. According to this theory, organic dust through space is
ready to infect any planet which offers the conditions under which
life may arise. Of course this theory does not explain the origin of
life. It pushes back that origin a little farther or supposes that
life is as old as matter itself. Again we may leave to the scientist
the discussion and the elaboration of this or any other theory he may
promulgate concerning the origin of life. When he has established
clearly the process and can produce life we will accept his
explanation; meanwhile, we will always be interested in his attempts
to solve the problem, but still our simple formula, "in the beginning
God," serves our present needs and will satisfy us better than any as
yet unverified hypothesis.

When we find through scientific investigation how life arises we will
simply know how God created it in the beginning.

The next step in the understanding of early life is to study under the
microscope the simplest forms which we can find in existence to-day.
This, while far easier of execution than the problems which we have
thus far considered, is still not without serious difficulties. But
every day brings us nearer to the understanding of the structure of
living things. Life the scientist cannot see. All he can study is
living matter. Whether life can exist separate from living things is a
problem outside the range of his, at least present, possibilities.
Therefore, concerning it he has no answer whatever to give. But when
we come to study living things we find that all life is associated
with protoplasm. This apparently foamy, jellylike, transparent
material is the only living substance in all the world. Animals and
plants are larger or smaller collections of the little masses of
protoplasm which we know as cells. The lowest animals are each made up
of but a single cell. This consists of a small mass of protoplasm
surrounded almost always by a thicker skin or covering, known as the
cell wall and enclosing a complicated kernel known as the nucleus. The
protoplasm seems to be the living substance itself. The cell wall is
not a simple dead scum on the outside of the protoplasm, but is itself
able to do certain things which can only, so far as we know, be done
by living substances. For instance, of two materials dissolved in the
water in which the cell floats, the wall may permit one to soak into
the animal and keep the other out. The one allowed to enter will
usually be found good to be used for food by the cell. The nucleus
seems to store within itself the record of its past history and thus
enable the cell to do in the future what its ancestors did in the
past.

Such simple cells can exhibit in very low form all the activities the
higher animals show in much more elaborate development. A one-celled
animal can move about, can recognize the proximity of food, can engulf
its food and digest it, can build up its own substance out of the
digested food, can absorb oxygen, can use this oxygen in the burning
of its own substance to produce its own activities, can act in
response to sensation gained from outside, can throw off its waste
matter produced by its own activities, and can grow. When the proper
time comes its nucleus can split in two, the cell itself enclosing the
nucleus can separate into two cells, each of which can grow to the
size of the parent cell and repeat its life. This is as simple an
animal as we have yet discovered. Every kitchen drain swarms with such
creatures. On a summer day the stagnant pools are full of them. The
simplest microscope will show them clearly. This is life in its lowest
terms with which we are acquainted. With such life, it seems to us,
the animal and plant world must have started their existence, when
first the earth began to teem with living matter.

If, then, we may form any judgment concerning the first living things
upon the globe by considering the simplest creatures that live here
to-day, certain facts seem clear. In the first place, life began in
the water, and for a long time was only to be found in the water.
Single cells are so small and dry out so easily that it is necessary
to their existence that they should be kept entirely moist by the
presence of water all about them. It is true many of them will stand
drying, but while they are thus dried they can scarcely be said to be
much more than just alive. They are utterly inactive, or, as we say,
they are dormant. In such conditions they become covered with a tough
skin, almost a shell, and their protoplasm is itself nearly dry. Under
these circumstances the life processes hardly continue at all. The
protozoa, as these small animals are called, tolerate drought for a
time; but they only live, in any sense worth calling living, when
water is abundant and is neither very warm nor very cold. It is safe
to say that the early life of the world formed in the oceans of the
time. So absolutely is the habit fixed upon cells of protoplasm that
even to-day the activities of the cells of higher animals depend upon
the presence of moisture. The cells of our own bodies are to-day
living, as it were, in an ocean. Everyone can remember far enough back
to recall some time at which a tear slipped from his own eye onto his
own tongue; we know our tears are salt. The tongue has tasted,
undoubtedly, the perspiration from the lip on more than one summer
day; this perspiration tasted as salt as the tear itself. The lymph
that constitutes the "water" of a so-called "water blister" is also
salty, and even the little blood one gets into his mouth in trying
nature's method of stanching the flow from a cut finger gives the
impression that it contains a little salt. Every fluid of the body is
salty, and every cell of the body is bathed in salt water. It is too
long since the ancestors of our cells swam in the seas of the Eozoic
time for us to assert with any positiveness that the ancestral habit
is responsible for this trait in the descendants. Sure it is that
to-day our cells, like their ancestors of old, live in water, and this
water is slightly salty--as were probably the Archæan seas.

The geologist tries as best he may to build up the geography of the
earth in the past. He endeavors to judge from the rocks as he now
finds them, where the seas, the bays, the dry land, and the mountains
of earlier geological times lay. The present aspect of the earth is
very recent, and earlier ages must have shown an entirely different
distribution of land and water. The North American continent was
certainly very much smaller than it is now. The first known lands lay
close to the Atlantic seaboard and probably extended out into the
water some distance beyond the present shoreline. The stretch of
continent was narrow, and grew narrower as it went southward. In what
is now the Canadian district, a considerable expanse probably existed
in very early times. Then a great internal sea, shallower than the
Atlantic, stretched its unbroken sheet over almost the entire area now
occupied by the United States, while only a comparatively small hump
of earth, ending in a narrower strip, lay where the great Western
plateau now rears its enormous bulk.

A large portion of the history of the North American continent, with
its developing animals and plants, is tied up with the gradual
shrinkage of this interior sea. Slowly across the Canadian district,
the Eastern and Western lands became connected with each other, while
the waters progressively were pushed down the continent, which was
steadily growing from the east and from the north, though less slowly
from the west, into this internal sea. To-day only the Gulf of Mexico
remains as evidence of the broad stretch that once extended through to
the Arctic Ocean and west beyond the present position of the Rocky
Mountains.

How this great Eastern backbone of the continent was produced, what
sort of animals lived while these rocks were being formed, or whether
this preceded entirely the existence of life upon the earth, no man
to-day may surely say. In the oldest of the rocks there are beds of
graphite, from which lead pencils are made. This substance is believed
by the geologists to be, like coal, the remains of vegetable life. But
these early rocks have been so heated and baked, so twisted and bent,
that whatever forms of life they once held are now obliterated, or so
altered as to give us no idea of what may have been their character.

So far as anyone can now see, this past history is wiped out forever
and it will be impossible for men ever to demonstrate the character of
this early life. Speculations, more or less certain, will arise. They
may, after a while, seem so clear as to receive the acceptance of the
scientific mind. Yet the truth remains that the early history of the
earth, so far as animals and plants are concerned, is probably lost
forever.

The most striking feature concerning the earliest layers of rocks in
which good fossils are found abundantly is the complexity of the life.
With the exception of the backboned animals, every important branch of
the animal kingdom is represented, and it is just possible that we
have even earlier forms of the vertebrates themselves. This, to the
evolutionist, is very disconcerting. To find the great groups all well
developed at least twenty-five million years ago and to find only
fossils built on the same lines since almost nonplusses him. When the
geologist tells him what an enormous length of time preceded the rocks
in which he finds these fossils and how absolutely these earlier
strata have been altered by the later geological activities he easily
understands why it is impossible to find fossils in them. As a
consequence, the evolutionist is forced to believe that all the
earliest animals have left no clear traces behind them. Life as he
first surely knows it is already extremely varied and quite well
developed in some of its groups. The early animals were as well
adapted to the times in which they lived as are the great majority of
the animals of to-day. The reader must not infer this to mean that
the animals of those days were like our present animals. They were
not. No one traveling in a far country could find there animals as
strange to him as would be those of the earlier stratified rocks. In
these there were no fishes as we know them to-day, not a single member
of the frog and salamander class, not a reptile, not a bird, not a
mammal, and probably no air-living insects. It is highly doubtful
whether there was any animal living upon the land and breathing the
air twenty-five million years ago.

We start our study, then, at the period known as the Palæozoic era,
the era of the ancient life of the globe, beginning twenty-five
million and ending ten million years ago. The first of the three
sections into which this period of life is divided is known as the
Silurian age, the age of invertebrates. The word invertebrate is an
unscientific but convenient term under which we embrace all the
animals below those having backbones. This period is called the age of
invertebrates because, although there is an enormous wealth of animal
and plant life in the Silurian, there are no backboned animals except
the lowest kinds of fishes. It was supposed for a long time that even
fishes were absent. Now we know they existed, but they were small and
inconspicuous. In this period corals were wonderfully abundant,
particularly in the great internal sea which spread over what is now
known as the Mississippi Valley. Everywhere over this region must have
grown in the shallow water great numbers of creatures called crinoids
or stone lilies. They were attached to the bottom by slender stems,
sometimes many feet long. These stems are jointed, and when they
became fossilized the sections were apt to separate, with the result
that over a wide area in the Mississippi Valley it is very common to
find these little segments which look not unlike checkers. At the end
of the stem was a rounded head, with a mouth at the top, and around
the mouth were branched, feathery arms. The creatures must have been
exquisitely beautiful, but they have completely disappeared from the
face of the earth, with the exception of a very few, found in the
obscurity of the almost fathomless depths of the great ocean. Here
they remain as peculiar relics, only preserved by the unvarying
conditions in the deep sea from the extinction that has met their
sisters.

Those who are familiar with our seacoast will know an interesting
creature known as the horseshoe crab, or king crab, though in reality
it is not a crab at all. It is rather more nearly related to the
spiders than the crabs, though no one but a technical zoölogist could
possibly associate them together. The ancestors of these king crabs
were the finest and best developed animals in this early Palæozoic
time. These creatures had bodies jointed like the tail of a lobster.
They were wide and flat, instead of narrow and rounded like a lobster,
and each joint of the body was highest in the middle and distinctly
lower at the two sides, thus forming three regions along their backs.
This structure gives to these creatures the name of trilobites. These
animals were the kings of the early ocean. They had an interesting
habit of curling up nose to tail before they died, and, as a result, a
large proportion of all the trilobite fossils we find are curled in
this peculiar manner.

After these forms the most abundant fossils we find in Silurian times
were creatures that at first sight looked as if they might be related
to the clams. These are known as lampshells, because one shell
projects beyond the other and curls up at the tip so as to resemble
the clay lamps which are dug out of old Roman towns. The lampshells
also have nearly disappeared in modern times. Simple creatures
belonging with our present crab and snail had begun to make their
appearance, but they were not as abundant as we find them later on.

The third group of the mollusks to which the nautilus and squid of
to-day belong is very abundantly represented in the Silurian by
fossils with coiled-up shells. As for the plant life of the time, it
is exceedingly difficult to say much about it. There must have been
nothing but marine plants, and these must have been on the general
line of the seaweeds. Little can be definitely said concerning them.

The next period of the Palæozoic is known as the Devonian age, or the
age of fishes. Now the backboned animals first make their clear and
unmistakable appearance. There are remains in the Silurian which show
that there must have been a few fishes at that time. The Devonian is
so full of them and they are so well developed and so diversified that
this period is definitely known as the "age of fishes." They do not
closely resemble the fishes of to-day, but anyone would recognize most
of them for what they are. Their bodies were covered, not so much with
scales as with heavy plates, often arranged like tiles, those on the
forward half of the animal being often larger than those surrounding
the rest of the body. The creature was encased, as it were, in armor.
These were the rulers of the Devonian seas. The land, as yet, was
probably nearly without animal life, the creatures thus far being
almost confined to the water. A few insects make their appearance and
a few thousand-leggers are running around among the lowly plants; a
few spider-like animals have arisen; there are a few snails that have
left the water and taken to the land. Altogether only the dawn of a
land fauna is to be noticed. In the Devonian the plants are creeping
up upon the ground. Ferns are growing about everywhere, though they
are not exactly our ferns, but are rather a sort of intermediate form
between these and the present seed plants.

Now comes an entire change in the history of the world. By some means
a rise in the bottom seems to have cut off a great part of the
internal sea from the outer ocean and to have converted it into a
widespread shallow bay, much like the sounds which lie back of the
islands that line the Atlantic Coast from New Jersey to Florida. Just
as this coastal region to-day is covered with salt marshes, so the
whole internal sea of the Carboniferous period was converted into a
great swamp. Sometimes an oscillation of the crust of the earth
brought this marsh above the surface of the sea and a luxuriant growth
of plants spread over it. Then a sinking of the bottom allowed the mud
and sand to wash down the shores, and spread out over the marsh, and
enclose the muck of the marsh under a layer of sand or clay. Another
lift of the bottom would start the swamp growing once more, and a
series of alternations between marsh land and sound seems to have
followed. The plants of this period are not the plants of to-day,
though we still have some very degenerate representatives of them. The
common horse-tail, with its angular, slender, leaflike branches and
its club-shaped spore-bearing body, is a modern degenerate descendant
of the treelike calamites of the Carboniferous forest. A creeping
evergreen, known by the name of clubmoss, is in like manner the modern
degenerate remnant of the scalestem and sealstem, which were the great
trees of the forests of the coal period.

All over the surface of the marsh, between these big trees, grew the
ferns. While the coal itself was formed generally from the scalestems
and sealstems, the most common fossils found in the shales that lie
upon the coal beds are the ferns which covered the surface of the
marsh.

It is believed by many geologists that this great luxuriant forest
points to a time when the climate was far warmer than it is to-day,
when the air was moist and heavily laden with carbon dioxide, and when
a great mass of clouds practically enveloped the earth. In this way
only do most geologists account for the enormous wealth of vegetation
in the Carboniferous period and for the abundance of plants up to the
Arctic Ocean, of the kinds that now grow chiefly in the tropics. But
of recent years a few geologists point to the fact that the peat bogs
of to-day, which seem to be the beginnings of future coal deposits,
are found almost entirely in cold countries. Hence it is a serious
matter to attempt to describe the climate of any part of the
Palæozoic era. Certainly of the climate earlier than the Carboniferous
it is very risky to say anything definite.

The forests of the coal period seem actually to have cleared the air;
at least now we begin to find creatures related to our salamanders and
frogs moving about among the stumps of the marshes. These amphibians
are evidently the descendants of some of the fishes of the Devonian
times. Among these fishes were some which bear a great resemblance to
a few found in South America, in Africa and Australia to-day, and
which we know as lungfish. Anyone who has cleaned our fresh water
fishes in preparation for the table will remember that inside of them
there is a long slender bladder filled with air. This bladder assists
in making the fish light, hence making it easier for it to support
itself in the water. In certain swampy regions these lungfish swim
freely in the water of the marshes. When the dry season comes,
however, the water evaporates, draining the marshes completely. This
would prove the death of most fishes. The lungfish have a curious
habit which keeps them over the dry season. They cover themselves with
a coat of mud, inside of which there is a lining of slime produced
from their bodies. In such cocoon-like cases they survive the drought.
The means by which they breathe during this dry season is
interesting. The swim-bladder which we have just described in other
fishes is, with this lungfish, peculiarly spongy in its walls,
presenting a large surface full of blood vessels which absorb the air
on the inside of the bladder. This air the fish changes with moderate
frequency, the result being that the swim-bladder serves him exactly
as the lung serves a higher animal. To this fact he owes his name of
lungfish.

We sometimes gain much light concerning the past history of any
particular form of animal by studying the development of that animal
in the egg, or, in the case of the mammals, before birth. It is an
interesting fact that when the lung begins to form in the embryo it
starts as a simple sac which is an offspring from the gullet, and
occupies the position of the swim-bladder of the fish. This sac later
divides into two, and develops into the lungs of the animal. This
assures the zoölogist that the origin of the lungs in the higher
animals is found in the swim-bladder of the so-called lungfish. In
this Silurian time certain of these lungfish were perhaps trapped in
the basin in the marsh by the uplifting of the border. The waters
becoming progressively shallower and more crowded, these fishes took
to the land, their fins developing into awkward limbs which slowly
became more perfect.

To state the fact in this simple fashion is to make it seem far less
probable than is really the case. The simple forms of the life of
lowly creatures, as well as the simple character of the legs and feet
in the salamander class, make the explanation not so unlikely as would
at first sight appear. Suffice it to say that the scientist now
believes that out of the lungfish of the Devonian came the amphibians
of the Carboniferous period.

At the end of the coal period came the greatest change the face of the
globe had seen for many millions of years. Slowly the continent rose
on both sides of the old interior sea. A great plateau formed in the
region of the Alleghenies and another in the western district, though
this latter uplift was to be completely washed away, and later to rise
again into the Rocky Mountains and the Sierras. With the uplift at the
edges of the continent came a steady rise of the internal marshes,
until what had previously been swamp land became progressively first
dry land and, in the western part, even desert, in that respect being
somewhat like what it is now.

The amphibians of to-day (animals like the salamander and frog) all
lay their eggs in the water and their young have a tadpole stage. This
doubtless was true of the amphibians of the coal period. With the
beginning of the Mesozoic, or "middle life" period, a change and a
progression comes over the animal world. The tadpole life of the frog
is a rather lengthened one, while the toad has learned to crowd its
tadpole life within a few weeks. It would seem as if, in the earlier
times of the Mesozoic, this same change of habit had been going on.
With the drying up of the swamp, some of the amphibians crowded their
tadpole stage further and further back, until it was completely
accomplished before their young left the egg. An examination of the
development of the reptile in the egg will show a stage very similar
to the fish and to the amphibians, but this is all experienced before
the reptile emerges from the egg. The reptilian egg, unlike that of
the frog, is covered with a shell, packed away under the surface of
the ground, and left to its own fate. If, as most geologists believe,
the climate of the Mesozoic was distinctly warm, this habit of the
parent of forsaking the egg was not a serious matter. However the
creatures arose, it is certain that in this Mesozoic age reptiles
roamed the forests, swam the seas, and even flew in the air. Probably
at no other time in the earth's history has any one class of animals
so completely dominated the situation as did the reptiles of this age.
They were not only abundant; they were frequently enormously large.
Their skeletons are among the most interesting that we find to-day.
Gigantic lizards, seventy feet long and eighteen feet high at the
shoulders, dragged their heavy bodies through the marshy edges of the
lakes. Out upon the land others, not quite so heavy nor so large,
roamed about, some of them feeding upon the soft vegetation, others
having teeth fitted to tear down their herbivorous cousins. In some of
them the hind legs and tail were very heavy and the front legs so
light that it is quite clear they must have hopped around as do the
kangaroos to-day. Others of these reptiles went back to the sea, lost
the leglike development of their limbs and regained the flipper form,
though the bones of the fingers and toes are singularly
distinguishable in the paddle.

Strangest of all, a considerable group of these wonderful reptiles
lengthened their little fingers, sometimes to three or four feet in
length, and had a skin stretched from these fingers over to the body
in such a fashion as to give them wings not unlike those of the bat.
In the wing of the bat, however, four of the fingers of the hand run
through the membrane and support it. In the pterodactyl, as these
flying reptiles are called, the middle finger supports the web, while
the remaining fingers can still be used to clasp objects or serve the
animal to lift himself, as the bat can do with his thumbs.

Meanwhile an entire change is coming over the plant world. The last
third of this age of reptiles is known as the Cretaceous or chalk
period. Now, for the first time, the forests begin to take on more of
the character of our forests of to-day. Plants like our willow and
beech, poplar and sassafras appear in great abundance. Their broad
leaves serve better than those of any earlier plants to catch the
sunlight. But in addition they offered such effective evaporating
surface that they cast off rapidly the moisture obtained from the
ground by the plant. Accordingly in the winter season, when the water
in the ground is frozen and not available for plant purposes, they
were forced to throw away their leaves. It is quite possible that up
to and including the time of the Carboniferous, plants were all
evergreen. There had been before this little variation in climate over
the globe. Life in the Cretaceous begins to take on distinctly its
modern form.

Among the reptiles of the forest there appear to have been a few small
creatures which to an observer of those times, if there could have
been an observer, would have seemed of the utmost insignificance
compared with their giant cousins.

These little creatures climbed up into the trees to escape their
enemies. There were some in whom the skin, in front of the elbow and
behind the wrist, was loose, and stretched across the joint a little
like the wing of a bat. This reptile, climbing into the trees to
escape its enemies, found that this loose flap of skin served it
nicely, and sailed out of the trees in a manner not unlike that of
the flying squirrel of to-day. Among these experimenters in aviation,
certain forms produced scales which became elongated and finally slit
up along the side. These slit scales slowly developed into the
feathers of the birds of to-day. Whether the steps by which the change
occurred have been correctly stated or not, the result is sure. In the
rocks of the chalk period we find the remains of an interesting
creature. If nothing but its bones had been found it would have been
called a reptile. It had a long tail, it had claws on its front limbs;
it had teeth in its mouth; it had a flexible backbone. All of these
are reptilian rather than bird characters. Yet on the rocks
surrounding these bones are the unmistakable impressions of the
feathers of the wings and of the tail. Nothing in the world to-day has
feathers excepting the birds, and in this "ancient winged thing," for
this is the significance of its name--archæopteryx--we have perhaps
the most remarkable link in the world between two distinct sections of
the animal kingdom. Here is a creature half reptile, half bird;
perhaps one-third reptile and two-thirds bird. It was about the size
of the crow. A little later unmistakable bird skeletons will appear,
but still their jaws are provided with long conical teeth.

Still more interesting from our standpoint is another set of primitive
animals, utterly insignificant in appearance, but of momentous
importance on account of their later history. Among these reptiles
were a few small creatures perhaps not much bigger than mice or moles.
Their teeth were a little more complicated and specialized than the
teeth of their reptilian cousins. Between their scales were small and
sparse hairs. Almost nothing but their jaws remain to-day to tell us
anything about them. But in this humble little creature of the
Mesozoic, utterly insignificant beside the tremendous reptiles of the
time, we discern the ancestor of the mammals. These were the
progenitors of the horses and cows, of the cats and dogs, of the
monkeys and apes, of the men of to-day.

During this chalk period, which forms the last portion of the age of
reptiles, life for the first time grew to look much as it does to-day.
Now, apparently, the cold of winter and the heat of summer followed
each other in regular succession. There have been colder and warmer
periods at various times in the previous history of the earth, but
undoubtedly they were more uniformly cold or uniformly warm than now.
Ages were warm, or ages were cold, but now the earth clearly shows the
annual alternations of summer and winter, and for the first time
clearly shows the bands of climate on the earth which we know as
zones.

In the chalk period this new factor of cold works mightily in favor
of the mammals. Their reptilian ancestors were cold blooded. When the
climate was warm they were active; when the climate was cold they were
sluggish. With the continuation of the annual alternations of cold and
warm weather that had now set in upon the earth, the little birds and
mammals had in their warm blood an advantage which, in the long run,
enables them not simply to compete with their reptile forefathers, but
to outdistance them absolutely in the race. Here and there, on earth
to-day, exist a few big reptiles like the crocodiles and the boa
constrictors. But they are few and comparatively insignificant among
the multitudinous population of the globe and are confined to the
hotter portions of the earth. For the most part, the reptiles now play
an insignificant and unobtrusive part. The little molelike creatures,
practically unnoticed between their feet in the later Mesozoic, have
come to supplant them entirely, and almost to rival them in size.
While the reptiles have grown steadily smaller, the mammals have
steadily become larger.

While there is no land mammal to-day as big as the heaviest of the
reptiles in the Mesozoic, the whale, which is one of the mammals that
has again taken to the ocean, surpasses in size even those gigantic
creatures. There never lived in the world before a creature quite so
big as the biggest of our whales. Size, however, is not the most
important point in any animal. Speed, sagacity, variability, and power
of adaptation, these are the qualities which the world prizes, and
these the new mammals possessed.

The next geological era is the Cenozoic, or period of modern life.
This is divided into two quite distinct sections, the Tertiary and the
Quaternary. This era began about five million years ago, roughly
speaking, and is still going on. The greater half of it is known as
the Tertiary. It was during this time that the mammals came to their
own. At first these creatures belonged to what the scientist knows as
generalized types. They are jacks-of-all-trades. The student of early
animal life finds in the little Phenacodus, which was scarcely bigger
than a good-sized setter dog, the beginnings from which many forms
have subsequently developed. This creature showed points of structure
which to-day may be seen in such diversified animals as the dog, the
horse, the rabbit, and the monkey. It is not, of course, suggested
that Phenacodus was the immediate ancestor of any of these. But there
were no animals in those times more like these I have mentioned than
was Phenacodus, and from forms like it in main features all of these
other animals have since been derived, each species of animal having
become adapted to one particular kind of life. The development of
diversified situations on the earth, the varieties of climate, the
variation between marsh and upland, between valley and plateau,
furnish a complexity of environment into each niche of which a new
form of animal fitted itself.

With the increased complexity of mammals comes the submergence of the
reptiles and amphibians to-day. In all sorts of situations we find
mammals. The old-fashioned continent of Australia is separated from
everything about it by deep water, impassable to any animal which
lives upon it. In this secluded country evolution is very slow and
animals are very antiquated. We still find there mammals with the
ancient habit of laying eggs in a hollow in the ground, though after
these eggs are hatched the young are nursed on the milk of the mother.
But on the great continental stretches, where competition is keen,
where the animal must battle for his life against a wide field of
other animals, where migration into new situations is possible, the
rapidity of the development has been very much greater.

It is in such a situation that man has arisen. In the extreme
southeastern portion of Asia, and on the islands lying close to the
coast, his highest non-human relatives, members of the ape family,
have reached their best development. These, of course, are not man's
ancestors. They are the less progressive members who are left behind
entirely in the race. Whether we have to-day any traces of the steps
by which man arose from the animal beneath him is vigorously disputed.
Eminent scientists will be found on both sides of this question.

Many scientific writers to-day take it for granted that one form,
discovered in Java, while it may not be in the absolutely direct line,
must be very close indeed to the line of ascent toward man out of the
apelike forms. A scientist by the name of DuBois, working in the banks
of a stream in south-central Java, found a thigh bone which seemed to
him exceedingly human in its general character and yet not absolutely
like the human thigh bone. The oncoming of the rainy season raised the
water in the river so that DuBois could not continue his search.
Returning a year later, and digging back deeper into this bank, he
found a skull cap and two molar teeth which seemed to him to belong to
the thigh bone, although they lay several yards farther back, but at
the same level in the bank.

When these bones were subsequently presented to a meeting of European
scientists by DuBois, he claimed to have found the "missing link" for
which there was so eager a demand. Some of the best anatomists of the
meeting, notably Virchow, laughed at his claim and said that the skull
cap was simply that of a human idiot, and could be duplicated in any
large asylum. A committee of twelve naturalists was appointed to
report upon DuBois' find. Of this committee three asserted the bones
to be those of a low-grade man, three insisted that they belonged to a
high ape, of a type somewhat higher than any we know to-day, but still
distinctly an ape. Six members of the committee of twelve agreed that
the remains were those of a creature higher than an ape and lower than
any normal man, and represented, in their opinion, a stage distinctly
along the line of development out of the apes and into man.

This so-called "Java find" is known in science by the name of
Pithecanthropus, which means the ape-man. Whether we look upon this
fossil as a serious find or not, it is very certain that in the caves
of Europe belonging to the Quaternary period we find abundant
evidences of primitive man. The older these evidences are, the more
likely they are to be distinctly below the grade of man of to-day, in
the size and shape of the brain case and in the length and massiveness
of the jaw.

There are probably more races than one represented among these skulls.
Some of them are surely well-deserving of the title of low brow. Their
heavy ridges over the eyes, their small foreheads, their massive,
heavy-set jaws show a race of men far less endowed mentally and much
better endowed in the matter of brute force than the men of to-day.
These skeletons, or parts of skeletons, are turning up every year, and
we are just beginning to know much about them. Capable men are
studying them with much care. The next fifty years may not improbably
make the history of the ascent of man as clear as is now that of the
horse, to which we shall refer later.

The whole question of the descent of man from the lower animals, or
his ascent from them, as Drummond aptly termed it, is to most people
so entirely repugnant as to set them at once, and finally, against all
willingness to consider the question of Evolution. This, however, does
not solve the problem. Even though truth be horribly unpalatable, it
is still to be believed if it is only the truth. There is practically
no doubt left among scientific men of the origin of man in lower
forms. The evidences grow more and more complete year by year, and
from every line of investigation. Whether we study his anatomy, his
embryology, his history, his language, or his civilization, all
indications point in the same direction. Constant discoveries indicate
the fact of an enormously long development from a very humble form. If
this proves to be true and remains unpalatable, the fault lies in the
palate and not in the truth. Gradually we are coming to understand
that there is no reason why this truth should be unpalatable. We
consider a rise from humble conditions to be the glory of our heroes;
we esteem it an added charm in their strength that they should have
developed from untoward surroundings. It is not a disgrace to man to
have descended from the apes. It is to the glory of man that he should
have ascended from forms not much more promising-looking than the apes
of to-day. We must repeat, however, that the apes were the
unprogressive members, and hence we must not judge man's ancestors too
harshly. It must have been in them to rise. But the great glory in the
thought of the humble ancestry lies in the possibilities of his
future. If out of a creature not materially unlike the gibbering ape
of to-day there should have come, under the guiding hand of an
Almighty God, creatures with the endowments and capabilities of man of
to-day, then this is only an earnest and foretaste of that which may
be expected in the future. A time will come when man shall have risen
to heights as far above anything he now is as to-day he stands above
the ape. Even then there seems no end. With Infinite Power as the
agent, and limitless time in which to work, man would be limiting God
to an extent unwarranted by the history of the past to imagine that
His process had stopped to-day, and that man, with his many
imperfections of body, of mind, and of morals, should be the best that
is yet to come. There cling to him still the limitations and dregs of
his brute life. Often the brute in him comes to the surface. Little by
little he is coming to be dominated by the qualities God has last
given him. Slowly the brute shall sink away, slowly the divine in him
shall advance, until such heights are attained as we to-day can
scarcely imagine. As we can scarcely conceive the beginnings of this
process, so we can with difficulty imagine its end. This only can be
seen by the Eternal through whom it shall all come to pass, and by
whom all will in time be accomplished.



CHAPTER VII

HOW THE MAMMALS DEVELOPED


When the idea of evolution first began to be much discussed,
especially after the publication of the "Origin of Species," there
were several points which appeared to be more than commonly difficult
of explanation. It did not seem impossible that the various types of
domesticated cattle should have descended from a common ancestor. It
did not seem difficult of comprehension that the dog might once have
been a wolf. Though not quite so credible, it did not seem absurd that
the tigers, lions, and leopards should have once all been alike. The
resemblance between these are strong enough to make the idea seem
conceivable. Though men were willing to concede this much, they
insisted that the great branches of the animal kingdom varied so
widely from each other as to make it certain that each was a separate
creation. It was particularly objected that the mammals differed so
entirely from other animals in several important particulars that a
special divine act was necessary for their appearance. The mammals
have a furry covering entirely different from the clothing of any
other animal in the kingdom, and have warm blood, which is found
nowhere else except among the birds. But particularly their method of
producing their young seemed so entirely different from that of any
other group that here a special creation was deemed absolutely
necessary.

Other young creatures are produced from eggs laid by the parent and
subsequently hatched. The young of the mammals are born alive and
comparatively well developed. In addition, their first food, the milk
of the mother, is so entirely different from the food of any other
creature that this again seemed to involve a separate creation.
Gradually we have come to understand the whole matter of reproduction
very much better. Minute and careful dissections of rabbits, of dogs
and cats, of animals slaughtered for food, with occasional post-mortem
examinations of human beings in various stages of the development of
the young, leave us no longer in doubt concerning the main features of
the process. The better we come to understand it the more clearly it
becomes evident that in the development of the mammals we have no new
procedure, but, as in so many other activities, new developments of an
old process.

There are two entirely different methods by which new animals and
plants may arise. One sees sometimes in the home of a friend a
geranium of particular beauty, the like of which he would be glad to
possess. The accommodating friend cuts a small piece from the
geranium. This is stuck into poor but well-watered ground, develops
roots, and eventually grows into a geranium stalk exactly like the one
from which it came and of which it is in reality only a detached part.

In similar fashion, if one wants a particular kind of apple, he never
trusts to planting an apple seed. Going to the tree of the variety he
desires, he takes from it a small twig provided with a bud and inserts
this bud into a cleft made in the young branch of another apple tree.
The young bud so inserted starts up into a new branch, resembling
almost absolutely, not the tree which feeds it with sap, but the tree
from which the bud was originally taken.

When we wish a particular variety of potato we obtain pieces of the
potato of the kind we desire. Each of these must contain an eye, which
is a bud of the old potato. When the sprout appears the new plant will
be practically identical in character with the plant from which the
potato was taken. This sort of reproduction, in which a piece of the
old parent grows up into the new generation, is called the asexual
method. But one parent is concerned in the process, and the offspring
are as nearly as may be like the parent from which they arose.

The gardener who wishes to obtain new varieties is not content with
this method. If he plant the seed of the potato the outcome will be
most uncertain. His seed must be taken, of course, from the fruit of
the potato, and most of these plants never fruit. Every grower of
large quantities of potatoes will have noticed occasionally, on the
tops of the plant, after the flowers disappear, a globular growth
looking not unlike a small tomato, but with a tendency to become
purplish green in color. This is the fruit of the potato and in it are
the seeds. When these are planted all sorts of potatoes are liable to
start up. Most of them will prove worthless. An occasional seed may
produce an uncommonly fine plant. This new variety may thereafter be
propagated from the tuber, as the potato itself is called, and the new
strain will be kept constant in this way. This method of using the
seed for reproducing the plant is called the sexual method, because
two parents coöperate in the production of the seed. The pollen came
from one parent and the ovule, which after fertilization swelled up
into the seed, came from another. By this combination of two
individuals new varieties become quite possible. Nature seems to be
more concerned in improving her strain than in maintaining her older
strains. In all of her lowest plants and animals she uses the asexual
method of reproduction. As we go higher in the organic world the
two-parent method becomes increasingly common. When we reach the
higher animals, and most of the higher plants, this plan of double
parenthood, the sexual method, alone is used.

In order that we may the more clearly understand how the mammals
produce their young and nourish them, we shall begin at the lowest
class of the backboned animals and note how the process is there
accomplished. As we pass upward through the kingdom the method
acquires greater complexity. When we finally reach the mammals, what
at first seemed an absolutely new process will prove to be, as is all
of nature's work with which we are thoroughly acquainted, but a
modification and an elaboration of some previously existing process.

Some time ago I was passing the early months of summer by the side of
a lake in northern Pennsylvania. Near my tent, on the edge of the
water, was a wharf from which it was possible to look down into the
shallows about the edge of the lake. In early July the bottom began to
take on a strange appearance. Spots as big as a dinner plate became
evident because they were cleaned of the finer sand or mud which is
common on the bottom. A close examination showed that each of these
circular spots was being occupied and cleaned up by a sunfish. The
pebbles were lifted into the mouth of the fish and driven out again
with force. The water which emerged with the stones seemed to wash
away the dirt, while the pebbles themselves became gradually cleaned
of the green plant life which ordinarily covers them. After the
process was completed each spot was saucer-shaped and free from scum
and mud. Over each of these spots hovered the sunfish which made it,
and round and round the fish swam. The circles thus traversed were so
near each other that every now and then the occupants of two adjoining
nests would meet on the border. The fish which was most nearly on its
own ground would at once attack the other and drive him away. In a few
days the other partner in each family seemed to appear. Now two fishes
swam side by side over each nest, bringing the lower edge of their
bodies comparatively close together. In this position they moved
around over the pebbly bottom. The female was discharging her
multitudinous and very small eggs, so that they dropped to the bottom
of the nest. At the same time the male was expelling what in fish is
known as the milt. In this milt are the sperm cells of the male, each
consisting of a rounded head and a very slender body. These are
attracted by the eggs. Pushing up against them, the head of a sperm
cell, consisting almost entirely of the nucleus of the cell and
carrying the determinants which were to decide one-half of its future
characters, penetrated this egg and fused with its nucleus. This was
filled with the determinants of the characters inherited from the
mother. Of course many of the eggs, of which probably there are a
thousand, must have escaped fertilization. There are doubtless a
thousand sperm cells that went to utter waste for one which found an
egg to fertilize. These eggs nestled in the crevices between the
stones in the warm water of the edge of the lake. Here the sun could
easily penetrate to the bottom and hatch them. The little fish, still
guarded by one hovering parent, swam around in the water long before
the yolk of the egg, containing its large amount of food, had been
absorbed into the tissues of the young fish. This fatty store made the
abdomen of the fish in which it lay protrude enormously. Gradually the
fish grew larger and the yolk grew smaller until all had been
consumed. Soon the fish began to forage for himself and no longer to
demand or care for the company and protection of its parent. The
little sunfish is highly favored among his comrades in having any care
whatever by the parent. In the case of most fishes the female,
swimming slowly over the bottom, deposits her eggs, which are
fertilized by the male, which follows behind her. After the eggs have
thus been laid and quickened no other attention is paid to them by
either of the parents.

Fish are stupid almost beyond the comprehension of those who are not
students of the minds of animals. Frogs and toads are a distinct step
in advance, and hence their mental activities play a larger part in
the process.

In the love-making of the frogs and toads the song has an important
share. In each species the voice is a little different from that of
any other. In our familiar garden toad we have an excellent
illustration of the method common to the entire group. When spring
comes an impulse seems to stir in all the toads of a neighborhood.
Heretofore they have stuck faithfully to dry ground; now they start
off for the water. Whether their impulse is simply to move down hill
or whether they by some means detect the near presence of water, I
cannot say. Certainly a new fountain on a lawn will secure in spring
its prompt and full share of the neighborhood's toads. In any event
the toads of a district congregate in great numbers in any pond or
along the edge of any moderate stream. Within a short time their
flutelike, quivering voice is heard far and wide. That this note has
an attractive power over the female there is no doubt. She herself
makes no effort to imitate, but the song of her mate is persistent and
exceedingly sweet. I have seen a male sit upon a clump of grass and
utter his love call. Before he had been singing for more than half a
minute three females hastened toward him from a distance of perhaps
twenty feet. Each seemed anxious to reach as promptly as possible the
creature whose voice had proved so attractive. When the mating comes,
the female discharges a series of small shotlike eggs which are
encased in a very tenacious mucous. While they are being deposited the
male fertilizes them. No sooner have the eggs, fertilized by the sperm
cells, reached the water than the mucous at once begins to swell. The
result is that eggs appear encased in two slender strings of jelly,
each having a diameter about that of a lead pencil. At intervals of
not more than half an inch the shotlike eggs may be seen. The mother
toad, in laying these eggs, moves about rather restlessly in the
water. By this means she succeeds in wrapping the strings about the
grass and sticks of the pool. This will hold them quite safely even
against a considerable current of water, should the stream rise and
flood the side pools in which the eggs are laid. With this amount of
care, however, the attention of both parents to the young entirely
ceases. They are now abandoned to the chances of a fortune to them
exceedingly unkind. A toad will lay about five hundred eggs. It is
evident that on the average only two of these can attain maturity by
the time the parents have died, for the number of toads does not
materially alter season by season. The connecting string is made up
not of nourishment for the eggs, but of a bitter mucous so unpleasant
to the taste that fish are thus deterred from eating the otherwise
nourishing material. This secures for the young embryo a chance to
mature which in the absence of the jelly it would entirely lack.
Imbedded in this mucous is the embryo itself, surrounded by a small
amount of albumen and containing inside of itself a very considerable
amount of yolk. This gives to the egg a volume possibly a hundred
times that of the egg of the sunfish. Thus, even counting the care the
parent sunfish took of its offspring, which care is very uncommon
among fishes, the toad stands a distinctly better chance in life. The
protection of the bitter mucous and the large amount of yolk
permitting considerably larger development before leaving the egg,
give to the toad a material advantage. When the toad first emerges
from the egg it is amazingly like the fish. It has gills at the side
of its neck and swims by the movement of its tail. Later its limbs
develop, the hind ones coming first, its tail is absorbed, and it is
now a true toad, ready to leave the water.

Altogether a higher state of reproduction is encountered when we reach
the reptiles, which are the next higher class of backboned animals.
Here very distinct developments of the process are discovered. The
turtle, to use the best known illustration, may lay but twenty eggs.
But she will not lay them at random in the water, as do the toads and
the fish. Each egg is wonderfully fattened with yolk. This means that
it is possible for the creature to develop to a far greater extent
before leaving the egg than was possible in the case of the toad.
Accordingly the little turtle, while it begins life not unlike a fish
and goes through the gilled and tailed period, during which it is not
unlike a tadpole, passes beyond this period before leaving the shell
and has already acquired its full turtle characters when first it
steps upon the scene. So big an egg as this would be highly nutritious
and animals would desire it immensely for food. Hence it becomes
necessary for the turtle to securely hide her eggs. In order to do
this, she scoops out a pit in the sand in which she deposits them and
here they develop. If no further provisions were made the eggs of the
turtle would dry completely and never hatch. Accordingly it becomes
necessary for the turtle to enclose each egg in a tough, leathery
membrane, known as the shell. Because the egg is thus encased it is
necessary for it to be fertilized before being laid. Accordingly the
male must place the sperm cells within the body of the female. These
cells swim nearly to the top of the tubes in which they are placed,
and there fertilize the descending eggs. Farther down the canal the
shell is secreted about the now swollen mass of yolk and white,
completing the egg just before it leaves the parent.

If the evolutionist understands properly the line of descent, the
birds and mammals are both the descendants of the reptiles. While
there is less exterior resemblance between a chicken and a turtle than
between a cat and a turtle, the real relationship in the first case is
much closer than in the second. This is perhaps most easily seen in
the scaly legs of both bird and reptile. Another remarkable
resemblance lies in the fact that in both cases the eggs are large,
well stored with nourishment, and protected by a resistant shell.

So few people know the turtle's egg that it will be better to describe
that of the hen, which it largely resembles. Underneath the hard shell
is a tough but flexible membrane which lies against the limey coating,
except at the blunt end, where a separation between the two gives room
for a bubble of air. Inside of this shell and its membrane lies the
white of the egg, which is nourishment for the chick, though not
nearly so rich as the yolk. This, besides the albumen which it
contains, is stored with large quantities of fat. It will be
remembered that upon breaking a hen's egg and dropping it into a bowl,
the yolk holds together because it is enclosed in a delicate sac. As
the yolk falls into the bowl there floats to the top of it a lighter
yellow spot as big as the end of a lead pencil. This is all of the egg
which thus far represents the chick itself. All the rest is
nourishment. This disk already consists of three reasonably
distinguishable layers of cells, which grow rapidly different from
each other. They spread and bend and twist, forming the young chick
and a set of organs which serve for its protection and maintenance
during its embryonic life. Within a few days these accessory organs
will have formed distinctly. Within the upper half of the yolk will be
found the small developing chick, which for the first thirty-six hours
of its development passes through a stage not unlike the fish, or the
earlier steps of the turtle. Within a few days it becomes clearly
evident that this creature is to be a bird, though it is much longer
before it is clearly a chick.

This embryo is so soft that it is almost like curd in thickened milk,
and could be very easily destroyed were it not for a protective device
which Nature has employed. It seems necessary that it should be
protected with the utmost care. The matter will be better understood
if we recall a common experience. Almost everyone has tried to
dissolve some substance in water in a vial. If the bottle be filled
with fluid to the top and corked it is very difficult to shake up the
contents. Even vigorous agitation produces little movement of the
material on the inside. If we wish to shake up the solid with water
the bottle must be left partly empty. The brain of a human being is
protected by just the same device. If it simply lay within the skull
the first fall would mash the gray substance against the side of the
cavity. To prevent this calamity the bony case is made somewhat larger
in capacity than the brain itself, and the space between the two is
filled with a watery fluid. This serves to prevent jars and shocks. In
the hen's egg the same plan is pursued. The embryo lies on the inside
of a bag considerably larger than itself. This sac, called the amnion,
is filled with a watery fluid. With such a protection only the most
severe shock to the egg would sufficiently jar the embryo to do it any
harm. The ordinary experiences of an egg leave it undisturbed.

Every living creature requires a constant supply of food and of
oxygen. The embryo is a living creature, and is no exception to the
rule. It needs an abundant supply of easily assimilated food and of
oxygen. When the hen's egg is first laid the entire contents, with the
exception of the little light-colored disk which floats on the top of
the yolk, form the nourishment. The disk alone is the living organism.
In the earliest stages the embryo receives its food by simple
absorption from the yolk. As the chick increases in complexity the
yolk at first grows swampy, with fluid trickling here and there
through the more solid portions. Thin walls form about these little
streams, thus producing blood vessels which cover the entire surface
of the yolk. These absorb the nourishment and turn it over to the
embryo. As the latter grows in size both the yolk and white diminish.
The embryo soon becomes larger than the remaining yolk and is attached
to it by a cord filled with blood vessels which enter the chick near
the center of its body. The abdominal wall has an opening at this
point. One of the later occurrences in the life of the chick, before
it breaks through the egg, is to have the last remnant of the yolk and
its sac slip to the inside of the abdomen, which then completely
closes over it.

As yet, we have seen no arrangement for furnishing air to the chick.
At the same point at which the blood vessels from the yolk enter the
chick, another set of vessels pass in and out. These are attached to a
large flattened bag which floats above the embryo against the upper
side of the shell. This bag is called the allantois, and serves as a
sort of lung for the developing chick. The shell is porous enough to
allow air to pass through it. The blood vessels of the allantois take
in oxygen and give out carbon dioxide through the porous shell. The
blood thus altered is returned to the chick and serves its life
purposes. One of the reasons why the chicken must turn its eggs in the
nest is that, if the allantois remain too long in contact with the
upper shell of the egg, it will become attached to it and will not
thereafter perform its functions.

The embryo thus enclosed in the egg finds its protection in the fact
that it is encased in a fluid contained in the amnion. It draws its
nourishment from the yolk upon which it lives and the nourishment is
transmitted to it by blood vessels. It draws its oxygen and throws off
its wastes through the instrumentality of the allantois, which covers
it over. Day by day the chick becomes larger, day by day it grows to
look more like what it is to be. By the nineteenth day it appears to
be complete. Its nervous organization is, however, not thoroughly
developed. If removed from the shell the chick still is indisposed to
stand upon its feet or to run about. If allowed to remain in the egg
until the twenty-first day, the chick will be able to push its beak
through the skin enclosing the bubble of air at the blunt end of the
egg and get the first breath into its lungs. Now it gives a faint
peep, breaks the shell of the egg, and steps out into the open air.

I have given this somewhat lengthened description of the development
of the chick because of the light it throws upon the method pursued by
the mammals. The features which have been described in the case of the
chicken's egg could be as fully observed in the case of the turtle or
any of the other reptiles. Mammals are descended from the reptiles of
the Mesozoic, and whatever peculiarities there may be in their method
of producing their young must be derived from the reptiles. If we wish
to know how the earliest mammals produced their young, we can only
judge by the lowliest members of the group that live upon the earth
to-day. The most primitive of these is the so-called Duckmole, of
Australia. This little creature has habits not unlike those of the
muskrat. It burrows in the bank of a stream, and makes a nest at the
end of the burrow, where it lays its eggs. This is one of the very few
warm-blooded, hair-covered animals which still lays eggs. A little
higher in the scale stand the kangaroo and the opossum. These
creatures keep the egg inside of the body until it is hatched. But
this happens in so short a time that the young animal is exceedingly
immature and as yet unable to stand the outside air. Accordingly there
is a double fold of skin on the abdomen of the mother, covering her
breasts. This forms a suitable resting place into which these young
are conveyed as soon as they are born and from which they do not
emerge for many days. The little creature instantly fastens upon the
nipple of the mother, keeping its mouth constantly in this position.
At intervals the muscles of the breast force the milk into the mouth
of the young, which is still too undeveloped to suck for itself. As it
gets older the little opossum or kangaroo emerges from the pouch in
the pleasanter part of the day and in the absence of danger. It
returns to the mother's pocket as soon as it becomes cold or a cry
from its parent warns it of its defenseless position.

These creatures are the lowliest of the class upon the earth. The
great majority of all mammals have elaborated a far finer plan, in
which the young are retained within the body of the parent until they
are quite able to stand the air. The length of this time varies in
different mammals from a few weeks to more than a year. The egg must
be fertilized before it leaves the body of the parent. If it should
fail in this it simply passes out and is wasted. If the fertilizing
cell reaches the egg before it has progressed far down the tube it
begins its development. The embryo forms for itself the sort of head
and tail and gill slits which would have served its fish or its
tadpole ancestor. Its limbs develop as little buds indistinguishable
from similar buds that would have formed fins for the fish or wings
for the bird.

Around the embryo there forms a sac, the amnion filled with a fluid
which serves to protect the young mammals exactly as the growing chick
was protected. Under the forming creature there hangs a small but
empty yolksac. This is an actual remnant, a reminder of the past, when
the eggs of the mammals were also packed with yolk and the growing
embryo secured its nourishment exactly as does the maturing chick. But
a new method has been provided for the mammal, and consequently the
yolksac, though it has not entirely disappeared, has no nutritive
content for the growth of the embryo.

The allantois of the chick now gains a new development and an altered
function. In the case of the chick it floats against the shell of the
egg and absorbs oxygen through the shell. Inside the body of the
mammal this is impossible, because the air is too far away. No shell
is formed about the egg because it is not to be laid. The tube of the
parent's body in which the egg lies becomes thickened at the point of
contact with the egg. It grows spongy and full of blood vessels.
Meanwhile the allantois is also growing spongy. These two tissues are
so closely pressed against each other that the blood vessels of the
transformed allantois mesh in with those of the thickened parent
wall. Thus the blood vessels of the mother are brought into close
contact with those of her offspring. Her blood seeps over into the
transformed allantois which is now called a placenta. From this it is
handed over to the offspring, which thus receives from the mother her
blood, and returns its own used blood for enrichment and purification.
So the allantois of the reptile has become the placenta of the mammal.
In the first instance it served only as an organ of respiration. Now
it has come to supply the embryo with rich blood containing both food
and oxygen derived from the mother. After the offspring is born this
thickened pad breaks loose, and subsequently is also extruded from the
body, forming what is known as the afterbirth.

Thus far we have spoken of the change in the method by which the young
are brought to such a stage of development that they can stand the
outer air. One of the improved differences between the mammals and
other animals lies in the method by which they nourish their young for
some time after birth. The very word mammals signifies an animal who
is in the true sense of the word a mamma. This name for mother is
given to her because of the fact that she possesses what are
technically known as mammary glands, or, in simpler language, breasts.
It would seem as if here we had an entirely new organ. No other
animal gives nourishment to its young in such fashion; all mammals do.
What is the origin of the habit? How did the organ arise?

A part of an animal's body that has the power to gather material from
the blood and pour it out in the shape of fluid is known as a gland.
Sometimes a whole organ does nothing else. Sometimes small glands are
scattered through, or over, the surface of another organ. There are
two kinds of glands in the skin of the mammal. The best known and most
frequently thought of are those which pour out the perspiration. These
have a double function. In the first place they assist in keeping the
temperature of the body uniform. When we are too warm they pour out a
watery fluid over the surface of the body. If the air is dry enough
and our body not too closely protected by clothing, this perspiration
passes off in the form of vapor. All evaporation requires heat, which
in this case is extracted from the body. So soon as the temperature
returns to its normal level the flow of perspiration ceases. The other
function of the sweat glands is to take from the blood some of the
waste matters of the body and pour them out upon the surface. This is
done in order that the body may free itself from substances which, if
they were to accumulate, would have a poisonous effect upon its
action. It is this function of the sweat glands which makes it
necessary for us to bathe the surface of our bodies with water. Dirt,
in the ordinary sense of the word, is not harmful to a sound skin. Our
reason for bathing is really to remove the wastes which we ourselves
have poured upon the surface of the skin. These, if allowed to remain,
soon decompose, like all nitrogenous substances, and become very
offensive. They may then be reabsorbed into the skin and nature's
effort to throw them off has been in vain. These glands, since they
contain waste matter, could not possibly yield food for the young.
They would poison and not nourish. Hence, whatever the breasts may be,
they are not altered sweat glands.

There is another set of organs in the mammalian skin. At the base of
each hair lies an oil gland. The function of these is to pour out a
substance which spreads along each hair and over the surface of the
body. The outside of the skin is always dead, and would easily crack
were it not for the constant secretion of this oil. In winter, when
the blood circulates less freely and these glands consequently pour
out less oil, the supply frequently runs short. If what little is
poured out is too frequently removed by washing, the skin becomes
brittle, and, on bending a joint, the epidermis cracks. The gloss of
the hair is due to the oil thus poured out. This oil becomes one
ingredient in the milk produced by the transformed gland. But there
is another important constituent. When one does unaccustomed manual
work the ordinary result is the formation of a blister. The epidermis,
or scarfskin, becomes detached from the dermis, or true skin, and the
space between the two rapidly fills with the fluid portion of the
blood, known as lymph. The fact that no blood vessels have been broken
in this detachment results in there being no red corpuscles in this
fluid. Wherever a cavity forms in the body lymph is liable to enter
it.

The milk glands of the mammals are modified oil glands. The fluid
which they now pour out is no longer exactly the old oil with the
addition of the lymph. Undoubtedly in the past the first milk was more
like this simple mixture. There seems no doubt that the breasts of
to-day are the enlarged and modified oil glands of earlier mammals. In
one of the most primitive of our mammals the young simply lick certain
bare spots on the surface of the mother's abdomen. As higher forms
arise there develops a smaller or larger mound with a distinct
projection, about which the lips of the offspring can easily fasten.
Lamarck would have said that the suction of the infant had produced
such a mound, and that this had been transmitted to later offspring
until it had grown to be the highly developed organ we now find, for
instance, in the cow. Since, however, we have come to disbelieve in
the transmission of acquired characters, this explanation will no
longer serve. We must content ourselves with saying that, by whatever
accident the nipple arose, the success of it when present determined
its selection by nature and its consequent persistence. With increase
in its function has come increase in the size of the glands. Lower
animals which, like the hog, produce a large number of offspring,
possess a large number also of these glands. With the diminishing
number of young and greater care of them as we rise in the scale has
come also a diminishing number of breasts in the female. Whether those
on the front of the body should persist, or those on the rear, depends
upon other factors in the life of the animal. Hoofed animals, perhaps
because their best weapon is the hoof and they can there best protect
their young, have retained them in the rear of the body. In the group
of animals known as the primates, including monkeys, apes, and man,
the habit of holding the young in the arms for protection has
determined the persistence of the breasts upon the chest rather than
the abdomen.

It is interesting to notice that the habit of the elephant of
protecting its young by means of its tusks has also resulted in a
similar position of the milk glands.

That the primates had once a larger number of offspring is confirmed
by double evidence. Even to-day the number of children at a birth is
often two, sometimes three, rarely four. The day before this was
written came the report of a case of five children at a birth, all of
whom seemed sound and all of whom lived. Still more direct evidence is
found in the fact that occasionally in the human female there are two
pairs of breasts, and very rarely three pairs. These are then disposed
in a double line down the front of the body.

The new plan of caring for the young is one of the priceless heritages
of the higher animals. As we rise in the grade of life the number of
the young produced at one time steadily diminishes, while the care
spent upon them increases. The shad may lay four hundred thousand eggs
and trust them entirely to their fate. The sunfish will lay a
thousand, by no means all of which can be fertilized, but it guards
them somewhat after deposition. The toad lays several hundred, stores
them with a considerable amount of nourishment, and protects them by a
bitter deposit of mucous. The turtle has reduced the number of eggs to
perhaps a score. Each of these is supplied with abundant nourishment,
so that the young may develop to considerable size and activity before
emerging from the egg. This material is enclosed in a firm protective
shell and hidden away from sight by being buried in the ground. In the
mammals comparatively few eggs are produced at one time. These are
fertilized within the body of the parent, are attached to the parent,
and absorb her blood. No shell is needed because nothing will kill the
developing offspring that is not likely to injure the parent. Not only
do the young feed upon the blood of the mother up to the time of
birth, but they are practically dependent upon this same blood after
birth. Though they do not take it directly from the veins, the milk
is, none the less, the transformed blood of the mother. This assures
the young of food as well as of protection. Best of all, the young are
provided with the companionship of the mother. Now for the first time
animals learn by example. Heretofore they have been born with a nearly
undeviating instinct; now intelligence begins to arise. They can
imitate their mother. Heretofore no acquired characters affected the
young. In the mammals, although the young cannot inherit the acquired
habits of the parents, they can get them by imitation, which serves
nearly as well.

There is, however, a more wonderful advantage that comes from the
close attachment between mother and offspring. This intimate
relationship brings about an affection of the mother for her young
heretofore unknown in the animal world. It is somewhat paralleled
among birds, but here the care of the nestling is less intimate, far
less maternal, than the care of the mammal for her young. As the
number of the young grows less and the care taken of them increases,
the intensity of the affection also increases. By the time we get as
high as the dog or the cat this fondness becomes a fierce,
self-sacrificing love. When we come to man, with his high intellectual
powers, with his deeper moral sense, we find a wonderful change. This
love of the mother for her child has grown into the finest emotion
possible to the human heart. It no longer is confined to the dependent
life of the child, but follows the offspring through its entire life,
guiding, guarding, shaping its destiny, handing on to the child the
treasured wisdom of the race. Influenced by the example of the mother,
the father comes to have a love for his children. It is not so strong
as that of the mother, nor so utterly unselfish, but it is still a
noble and exquisite love. Developing in a different direction, the
love of the mother for her children grows as civilization advances,
and spreads over the father of those children as well. Again
reflecting her love, the man finds himself filled with a new feeling
for the woman. It is never as unselfish, as free from desire, as is
her love, but it completely transforms his relation to her. What has
been with him simply desire is ennobled and enriched until it becomes
the finest passion of his life, absolutely transforming him, in
relation to her, from a selfish brute into a tender and life-long
companion. So utterly does the love thus engendered transfigure human
life that when we seek to express the divine nature in human terms,
and these are the only terms we know how to use, the richest
revelation that has come to us is the conception taught by the Master
that "God is Love" and that "as a father pitieth his children, so the
Lord loveth them that fear him."



CHAPTER VIII

THE STORY OF THE HORSE


Ever since men have been familiar with the idea of evolution there has
been a temptation on the part of the zoölogist to draw up pedigrees
expressing the relationship between the various groups of the animal
kingdom. The impulse is natural, and, if the resulting tables are not
accepted with too much confidence, the result is not undesirable. The
truth of the matter is that all of these pedigrees are more or less
hypothetical. They simply show what connection seems most likely. In
all of them are spaces filled with doubtful names. Each addition to
our acquaintance with the past history of animals necessitates
revision of our tables. The student of fossils, trying to rebuild in
imagination the world of the past, finds himself often strangely
unable to link these animals together. The result is that the more we
know of fossils, the more distrustful we become of the easy
connections we have been making between groups. Accordingly we are
more than commonly pleased when we find the clear indication of a
genuine pedigree, actually illustrated by real examples, following
each other in time through the geological history. A few of these
lines are gradually becoming plain, and none of them is clearer than
the pedigree of our familiar and much loved horse. The example is a
particularly interesting one, not only because of our affection for
the animal, but because the horse originated in all likelihood in
North America on the land occupied to-day by our Western plains. As
though he loved the country of his ancestors, he returned after having
circled the globe, and once more went wild in the home of his
forefathers. The problem was first worked out in Europe and later
elaborated in this country. Now the history gets its finest expression
in the American Museum of Natural History in New York City. The
collection of fossil horses in that institution surpasses in
completeness and in excellence of mounting and of sympathetic
restoration any similar collection representing the ancestry of any
other animal in the world.

In the table of Geological Times, given in chapter six, the era of
recent life known as the Cenozoic is seen to occupy something like
five million years. This figure, as was previously suggested, is very
uncertain, and may be three or may be six, but is safely represented
in millions. Through most of this time stretches what is known as the
Age of Mammals, the Tertiary Age. Its close, occupying only the last
few hundred thousand years, is known as the Age of Man, the
Quaternary. Through perhaps three or four millions of these years
stretches the known pedigree of the horse.

When we go back to the early Tertiary we find a forest, with trees
that shed their leaves, interspersed with glades, in which already the
grasses were beginning to be developed. This state of affairs had
existed but for a comparatively short time, geologically speaking. It
had come only in the latter part of the preceding era. Lake and swamp,
meadow and forest intermingled to make a rich and varied scene. Slowly
the land toward the western side of North America lifted itself into
plateau and mountain range. Slowly the westerly winds began to be cut
off by the barriers thus raised across their path. As they swept over
the plateau and down into the eastern plain their moisture came to be
diminished. Gradually a very different state of affairs set in. The
ground became harder, the forest became sparser, the plants became
higher and firmer, the grasses tougher and more wiry, and, by the time
the Quaternary arrived, a condition probably even drier than that of
to-day existed over our western highlands. Throughout this long
change, spread over millions of years, a creature which has become our
horse steadily persisted and steadily advanced. Side lines developed
which finally disappeared, but the main line kept on, and when the
Quaternary came the horse arrived with it. Many of the skeletons in
this series were known before it was realized what they were. As time
went on and intermediate forms were found, it became possible to
recognize these as ancestors of the horse and to assign them their
proper position in the family tree.

[Illustration: THE EVOLUTION OF THE HORSE'S FOOT

_After H. F. Osborne and Charles R. Knight. By permission of the
American Museum of Natural History._]

The earliest of the forerunners of the horse with which we are
acquainted would certainly not be recognized as such by any but the
most careful student of animals, if we could see him to-day. He stood
not higher than a fox-terrier dog, though his shape was very
different. But he would probably be more likely to be classed with the
dog than with the horse by the hasty observer, for he walked with four
toes of each foot upon the ground as the dog does to-day. Like the
dog, he had hanging at the inner side of his front foot a little
useless toe. He was long in body, comparatively short of leg, a little
long of head and neck, and distinctly long of tail. His grinding teeth
had points on them not unlike a pig's, and possessed no apparent
resemblance to the wonderful curved and ridged surfaces seen on the
teeth of the modern horse. What his skin and hair were like can only
be conjectured. In the restoration which Mr. Knight has made, at the
suggestion of Professor Osborne, an interesting inference has been
drawn. That he was a creature of the forest is suggested by his
spreading toes, which would keep him from sinking in the soft soil. It
is consequently surmised that he was dappled with spots which allowed
him to rest unnoticed on the sun-flecked floor of the forest. Mane he
had none, and his tail was probably tufted slightly at the end with
hairs, which were increasingly short as they approached the top. He
had no forelock, and the hair along the ridge of his neck was a little
longer than the rest, and stood erect. Browsing about on the soft and
tender herbage of his woodland home, his teeth had as yet no tendency
to become specialized. The molars had mounds upon them, developing,
perhaps, more into the shape of the points of the hog's, but even
still quite generalized teeth. His main enemies, from whom, perhaps,
he could with little difficulty escape, were creatures related to the
hyenas of to-day. Perhaps, like their modern representatives, they
preferred eating their flesh tainted to exerting themselves enough to
capture and kill their prey. By the time we advance a little further
into the Tertiary, though still in its early portion, a remarkable
change has already come about. The fifth toe, which in the earliest
horse hung upon the side of the front foot, has completely
disappeared. The change in the hind foot has gone still further. The
hind leg in many animals evolves more rapidly than the front. The
heavy work of running is always done by the hind feet, while the front
feet serve rather as a prop to keep the animal from falling than as
the actual means of locomotion. Hence the hind feet and the muscles of
the hind quarters are almost always heavier than the front. Possibly
on the front foot the little fifth toe was less of an obstruction, and
persisted after the early horse had lost the corresponding toe on his
hind foot. This process has gone on still further in this second
stage, and the hind foot has but three toes, while the front still
has four. This is not the only advance. Already the middle toe of the
original set of five is becoming emphasized. The weight is thrown more
forcibly upon it, as with the human foot it is upon the inner or big
toe. The middle toe is growing larger and larger, and the nail upon it
is spreading around it and is growing firmer. The creature, too, is
standing more nearly upon his toes; his legs are getting longer; he
stands higher from the ground, and now has come to be the size of a
hound.

We can only surmise why this creature should have undergone such a
change, but the presence of flesh-eating animals having the size of a
fox, and presumably of the fox's swiftness, probably tells the story.
The little bands of early horses, pursued by their carnivorous foes,
were slowly modified into swifter creatures. It is not so much that
running made them fast, as that the slow ones were continually being
caught. If this process of constant elimination of the slow members of
any herd is kept up long enough, the group will necessarily develop
speed. As time goes on, of these early horses those which happened to
have longer legs and stood higher upon their toes won in the race, and
handed on their qualities to their long-legged descendants. As the
animal rose upon his toes, the inner toe, corresponding to our thumb,
was first raised off the ground and rendered useless, while a similar
change came over the corresponding toe on the hind foot. The hard work
of running being done on the latter, this superfluous toe was more
detrimental there than on the front foot, and disappeared,
consequently, more rapidly. In time, however, it also disappeared from
the front foot. Gradually the further elevation of the foot lifted the
toe, which corresponds to our little finger, off the ground, and this
now disappears also.

With increasing toughness of the grasses, as the climate becomes drier
and the region more elevated, the teeth of the horse are given harder
work. The points begin to spread into ridges and to unite with each
other in such way as to form the crescents, which are later to be so
characteristic of the teeth of the modern horse.

By the middle of the Tertiary this ancestral horse has risen in height
until he is taller and heavier than a setter dog. Three toes are found
on each front foot. The middle toe is getting constantly more
developed, though the smaller toes are evidently still of use. The
ridges of the teeth are quite crescentic now on the outer side, and
becoming better adapted to the evidently firmer food which the
creature is obliged to eat.

As we come toward the end of the Tertiary, the development which had
been all pointing in one direction has advanced very much further. The
creature now would be undoubtedly recognized by anyone as a horse. The
legs are longer and straighter; the middle toe has become the only
useful toe, though on each foot a smaller toe, slender and probably
useless, still hangs on either side. Two similar useless toes to-day
hang at the back of the foot of the cow, which is now walking upon her
two toes, which give her the appearance of carrying a cloven hoof.
That is to say, the first toe on the foot of the cow has disappeared,
the second and fifth hang useless and much diminished at the back of
the foot, while the third and fourth are both well developed and
serviceable in walking.

The late Tertiary horse has grown to be the size of a burro of to-day,
though probably it was a little more slender. The teeth are quite
horselike, both in shape of the crescentic ridges on their surface, in
the length of the teeth in the jaw bone, and in the fact that the
crinkled edges of enamel on the upper surface are protected on either
side by dentine or by cement. These surfaces, being softer than the
enamel, wore away somewhat more rapidly and allowed the sharp edges of
enamel to stand up in ridges. This plan increases the grinding power
of the teeth.

With the oncoming of the Era of Man the horse reaches his modern
splendid development. During the early Quaternary the horse was
perhaps in some of his representatives a larger creature than he is
to-day. Each foot now has but a single toe. The nail has spread around
firmly and heavily, until it has become a splendidly developed hoof,
permitting the animal to travel with speed over firm and often stony
ground. The side toes have disappeared completely from the outside of
the horse's leg, although upon removing the skin it is easy to find
the long splints, which are the remnants of toes, which have not yet
quite disappeared. His heel has been lifted in the air until it is
eighteen inches off the ground, and he is standing like an expert
dancer upon the tip of his toe. The body of the horse thus being
lifted far off the ground, a new development becomes necessary. All
through the growth of the creature the neck and head have been obliged
to lengthen correspondingly. Every animal must be able to bring its
head down to the level of its feet in order that it may drink. Various
animals use different methods to accomplish this result. The giraffe,
with his enormously long legs, has a correspondingly long neck, which
lowers his mouth to the ground. Even with this extended neck the
giraffe's legs are so exceedingly long that he is obliged to spread
his front feet when he wishes to reach the ground with his head. The
elephant has pursued exactly the reverse plan. Using his tremendous
head as a battering ram in fighting, and using his enormous tusks both
in battle and in uprooting young trees, a lengthened neck is
absolutely out of the question. Furthermore his front teeth have grown
so prodigiously that they would interfere with his getting his mouth
to water. Accordingly, his nose has lengthened its tip until it
reaches the level of his feet, and this nose becomes to him the main
organ of grasp and of touch. To drink, its end is inserted in the pool
and water is drawn up the nostril. If the animal were to attempt to
draw it all the way back into his throat, it would inevitably strangle
him by getting into his windpipe. Accordingly, when the nose is well
filled with water, the tip of it is inserted in his mouth, and the
water discharged by a quick puff. The horse has taken a method
intermediate between these. It had moderately lengthened both neck and
head in order to get to the ground with its nipping teeth, and thus to
gather the grasses which serve as its principal food.

The mammalian teeth, while of four kinds, really in most animals serve
but two purposes. The front teeth consist of the incisors and canines,
and are used for biting. The hind teeth, consisting of premolars and
molars, are used for grinding. In the horse, the jaw has lengthened
between these two sets, carrying the biting teeth far forward of the
molars. It is this gap in the row of the horse's teeth which makes it
possible for us to insert the bit into his mouth.

Now comes a strange accident into the life of our American horse.
Creatures of the same kin had been evolving in Europe and Africa, but
the developments are more distinctly horselike, it would seem, in our
own country. Then for some reason the horse disappeared completely
from American soil. Doubtless two things happened. First of all, some
of them migrated across a stretch of open country which then connected
America with Asia in the neighborhood of Bering Strait. These
creatures spread first over Asia and then over Africa and Europe,
leaving their skeletons scattered over this enormous stretch of
country. Asses and zebras are still found abundantly and widely
scattered, but the wild horse of to-day is seen only in western Asia.
What happened to those who remained in America we shall possibly never
know. Some surmise that a fly not unlike the tsetse-fly of Africa
killed them out. Perhaps the members of the cat family, which are
steadily growing larger and fiercer, fed on their young if not upon
the older ones, and exterminated them. Perhaps the Glacial period
which followed was too cold for them. But, whatever may have been the
cause these horses died out not only in North but also in South
America, to which country they had spread.

The old world horse was the companion of man. The skeletons of those
found with early man in the caves of Europe look as if the horse had
been a creature to draw man's burdens and to serve him for food,
rather than to bear him upon its back. Its roasted bones are often
found about the old tribal fires. Upon the discovery of the new world
the Spaniards brought with them to Mexico and to the Mississippi
Valley the horses which carried them in their battles against the
Indians. In the course of these frays many riders were killed and
their horses roamed wild. Slowly they made their way to the western
plains; gradually they became tougher and more wiry; their diminished
hoofs learned to catch more carefully in the rocks of their mountain
home; and the mustang and bronco of more recent years are the
descendants of the little dawn horse, whose dainty skeleton is found
in the rocks over which his later descendants, after a long stretch of
perhaps four million years, are now running.



CHAPTER IX

EVOLUTIONARY THEORIES SINCE DARWIN


In considering the value of Charles Darwin's work and its permanent
effect upon the thought of mankind, we must be careful to distinguish
between two phases of his effort. It was his aim to prove two
propositions: first, that there is such a process as evolution;
second, that he had discovered the method by which evolution is
accomplished. Before his time there was no general agreement as to the
fact of evolution. People generally thought the idea absurd, as well
as irreligious. All previous efforts on the part of advanced thinkers
to persuade mankind of the truth of evolution had been nearly without
effect. Among the early philosophers the whole idea was purely
speculative. They made no attempt to prove it, and the conception was
without influence upon the thinking of the ordinary man. This remains
true until the time of Lamarck. This French genius succeeded in
persuading not a few people of the validity of the idea of evolution.
He probably could have convinced many more had it not been for the
hostility of Cuvier. Accordingly, Charles Darwin's "Origin of
Species" fell upon a world entirely hostile to the idea, when it
thought of it at all. Within fifty years of the publication of this
wonderful book, probably the entire scientific world is agreed that
evolution, in some form or other, is the undoubted solution of the
mystery of creation. The materialist may think of it as a mechanical
process relentlessly working itself out without design or purpose. The
theist will accept it as the plan by which Eternal Power steadily
works. The devout Christian or Jew will see in it God's method of
creation. The idea of development has penetrated every science that
has to do with animals or man. It is even beginning to influence such
inorganic sciences as Physics and Chemistry. We now hear of the
evolution of the elements, and the evolution of forces. The world has
been persuaded that evolution is true, and this is primarily the
result of the work of Charles Darwin. It is astonishing that so great
a revolution should have come in so short a time.

The other phase of Darwin's work was his attempt to find the agent
which is bringing about the actual transformation of animals and
plants. As we have seen in the preceding chapters, it was his idea
that natural selection was the efficient agent which constantly
eliminated all unfit variations, leaving only the best to carry on the
work of the world and to reproduce their own fit kind. Many
biologists since his time have doubted whether unaided Natural
Selection will account for the constant advance in organisms. This is
the part of the work which is often seriously questioned.

Weissman and his co-workers have contended that this unaided principle
will serve. Most biologists have asked for some more efficient cause,
and assert that selection does not account for the appearance of
variations, but only for their preservation, and that any valid theory
of evolution must show how variations originate. It is chiefly in this
respect that Darwin's work has failed to satisfy many later
biologists. When we hear a scientist speak of Darwinism as being dead,
this is what he means. He does not think evolution false, but believes
that Natural Selection is not sufficient to account for evolution.
There are three main difficulties involved in Darwin's theory. The
chief defect lies in the fact that selection cannot originate
varieties. In all his earlier works Darwin simply accepted variations
as he found them. He was content to say that all species varied
constantly, and in every direction. He gave no theory to account for
variation. Whenever he took measurements of the dimensions of any
large series of objects of the same kind he found these measurements
to vary, apparently, in all directions. Upon the facts of these
variations, and without accounting for them, he built his own theory
of evolution. He realized his weakness, and acknowledged it in his
book. He probably did not anticipate how insistently later biologists
would demand an explanation that would account for this variation. In
his later work, responding to this criticism, Darwin originated a
theory which he called Pangenesis. He believed that when an adult
animal had responded to his environment and acquired a new character
he could transmit this character to his offspring. At that time no one
doubted this fact. The whole theory of Lamarck was based on the
assumption that this could be done. Darwin suggested that every organ
of the body threw off minute particles, which he called pangenes.
These little bodies, carried by the blood, were taken up by the egg
cells or sperm cells, and the latter cells determined the future
development. Consequently, the character of the new individual was
determined by the parental pangenes. In this way the gain acquired by
one generation could be passed on to the next. This theory was purely
speculative. He never pretended that there was the faintest
corroborating evidence visible to the microscope in the organ, in the
blood, or in the germ cell. It was not an accounting for what is, but
for what it seemed possible to him might be.

This theory of Pangenesis, in the shape in which Darwin promulgated
it, has dropped out of consideration almost entirely. DeVries of
recent years has revised it, but with distinct modifications, and most
biologists pay no attention to it.

There is a school of biologists, headed by Weissman, who have come to
be known as Neo-Darwinians. These men have insisted that Natural
Selection, if properly understood and developed, is quite sufficient
to account for the fact of evolution, including the appearance of
variations. Weissman himself is a microscopist of more than common
skill. He is thoroughly accomplished in the most modern methods of
killing, fixing, staining, and mounting. This worker's acquaintance
with the intimate structure of the cell is probably as great as that
of any other man in the world. Weissman asserts that he has seen
inside the nucleus all the machinery necessary to explain how the
father hands over his qualities to his children. He insists, equally
strongly, that this process is such that no father can hand to his
child any qualities which he himself did not have at least in
potentiality at his birth. Everything the individual acquires during
his lifetime is his own possession, which he may use and develop to
the utmost extent, but it dies with him. His children, born after he
possesses it, can no more inherit it than those born before. Weissman
expressed this in his famous statement that "There is no inheritance
of acquired characters." The biological world has had no shock equal
to this since Darwin's time, and there are few other questions to
which scientists to-day return with such constant vigor.

If what Weissman says is true, that no variation or development which
comes to an animal during his lifetime can be transferred into his own
germ cells and handed on to his children, then it becomes evident that
we must find some cause of variation that acts within the germ cells.
This is the difficulty which Weissman meets. He says that there are
small particles in the nucleus of each cell; that these particles
which he calls determinants decide the form and the course of
development of that cell; that when that cell divides to produce
another cell it gives to this other cell one-half of each determinant.
As a result the second cell grows to be like the first. This tells us
why offspring are like their parents. There is nothing in the theory
thus far to show us why offspring are not exactly like their parents.
In other words, there is no accounting, thus far in the theory, for
variation. When the biologist studies carefully the history of an egg
while it is being formed, he sees that at one stage in its development
it throws away not one-half of each determinant, but one-half of the
determinants. When an egg does this, it deliberately casts aside
one-half of the possibilities of its own development. This throwing
away is quite as effective for all its descendants. Any ancestral
quality now lost is lost from the line forever. In the formation of
the sperm cell set free by the male a similar throwing away of
one-half the characters has taken place. The egg cell and the sperm
cell fuse together. There are as many possibilities now as there were
in either parent, but not all the potentialities of both parents. Half
the possibilities of each have been thrown away, and hence cannot
appear in the offspring. By this constant process we get, in every
generation, new combinations of qualities. This is the main cause,
says Weissman, for variations.

There is, however, another possible cause. Each cell has enough
determinants in it for many individuals, and it seems to be more or
less a matter of accident which qualities shall come out. It has been
suggested that as an egg lies within the gland, a blood vessel may
bring blood to it in such way that a determinant, lying in a certain
position in the egg, may get the richest supply of blood, and hence
develop at the expense of the less nourished determinant. By these two
methods variation comes into an animal's life, if Weissman and his
school are to be believed.

This is a serious blow, if true, to many theories of evolution. The
great mass of evolutionists still feel that somehow there is an
influence by which the environment produces variation. How the
influences of the surrounding world can get down into the body of the
parent and affect the egg is unknown. This is freely confessed by
every biologist. All are agreed that Weissman's work has made us
cautious, and prevented our lightly accepting a belief in the
influence of the environment. Yet it is felt by many that slowly and
gradually, in the long run, the germ is affected in the same manner as
is the body of the parent. In other words, even those who are not
followers of Weissman, have accepted the idea that there is little
inheritance of acquired characters. Yet they return to the belief that
somehow, in some way as yet unexplainable, the main cause for
variation in animals lies in the situation in which they live, and
tends toward better adaptation to that situation.

Whether men with this conviction are merely reactionaries whose
confidence is returning, or bold thinkers whose views will ultimately
prevail, time alone can tell.

A second strong objection was brought against the theory of Natural
Selection. Darwin declared that small variations in favorable
directions are selected and become the starting point of new and
better things. It is soon seen, however, that the effect of unaided
Natural Selection would be but to mix new departures with the old
forms, and soon swamp out any progressive tendency. Whenever a genius
appeared, instead of finding a corresponding genius with which to
pair, it mated with the average of its own species. Hence its
offspring were nearer the average than it was, and their offspring
still nearer. Thus whatever advantage the genius originally possessed
gradually sank into the common level.

It was Moritz Wagner, a German naturalist, who first insisted that if
favorable variations were to amount to anything these possessors must
not only mate with others of their same kind, but must also be
prevented from mating with the old average group. Accordingly, the
belief arose that, under ordinary circumstances, variations returned
to the common level. Wherever a varying group became separated by any
barrier from mating with the rest of its species, and had only its own
kind to pair with, a new species sprang up. This barrier might be a
desert, or an impassable mountain range, an arm of the sea, or
anything else that the animal could not, or would not, cross. Isolated
in this way, the little group that had an advantage in a different
direction could develop its tendencies, and a new species would be
made of what had been previously only a geographical race. In this
matter of geographical isolation Wagner is very strongly supported by
the American zoölogist, David Starr Jordan, who believes that no two
closely related species of animals ever occupied the same geographical
area. Both Wagner and Jordan are ardent admirers of Darwin and his
theory of natural selection, but both believe that it is necessary to
add the idea of isolation in order to make natural selection
effective.

George John Romanes, a British naturalist, has added to Wagner's idea
of isolation, the expanded conception that there may be isolations
that are not geographical. For this phase, Romanes has coined the term
physiological isolation. Something in the structure or habit of the
animals with the new variation prevents them from mating with the
older type. Occasionally it is a difference in the structure of the
reproductive organs themselves. This, however, is not the only
possible divergence. The mating season in one group may come earlier
than that of the other, or may come during the day, while the main
group is in the habit of mating at night. Anything which keeps some
members of a species separate in their mating from the rest, will
result in the course of a longer or shorter time, says Romanes, in the
formation of a new species.

A third great objection was raised against Darwinism. The theory said
that only useful variations were selected by nature. It was asserted
by objectors that the earliest beginnings of any variation must be
too slight to be useful, or as the term went, to have selective value.

It has been noticed by a number of naturalists that certain animals
seem to carry the development of a peculiarity altogether too far. It
is seen for instance that in the Irish Elk, which has for some time
been extinct, the horns were so enormous as to be a source of danger
rather than of assistance to their owner. It was said that the
tendency to produce heavy horns had gained, as it were, a sort of
momentum, and that this impulse had carried the development beyond a
safe limit. The Irish Elk became extinct because his horns were too
heavy. During the Mesozoic period the reptiles grew too large. They
seemed to have carried size to a point at which it became a danger
instead of a help. They completely passed out of existence, leaving
behind them only very much smaller reptiles.

Eimer, of Germany, has based on facts like these his theory of
Orthogenesis. He says that variations in animals are not indefinite
and in every direction, but that they follow along clear and definite
lines. These lines, in the case of the elk and of the Mesozoic
reptiles, developed too far, but ordinarily the effect of such a
tendency is distinctly beneficial to the animal. It particularly
assists in carrying on for a time the variations which have not yet
become useful to the animal. It has always been difficult on Darwinian
principles to understand how the beginnings of the useful variations
could be selected before they were strong enough to be of actual value
to the animal. This tendency to variations in certain directions
instead of at random would account for such early development. This
theory of Orthogenesis has not figured very strongly in the history of
the movement, but it recurs at intervals.

Both in America and France there is a constant tendency on the part of
zoölogists to return to the Lamarckian idea that it is the use of an
organ that develops it, its disuse that makes it fade away. This is
undoubtedly true of the individual, and although Weissman insists that
it is useless to the species as a whole, many zoölogists are slow to
relinquish entirely the idea that somehow these favorable developments
become reproduced in the offspring.

Professor Cope, the American paleontologist, was a strong believer in
the effect of activity, both upon the individual and upon his
descendants. He believed that the insistent beating of the foot of an
animal upon the hard soil of the drying Tertiary plateau, had
influenced the production of a firmer nail, which spread around the
entire end of the toe and made the hoof of the ungulate. He believed
that the use of the teeth in grinding produced a stronger and better
molar tooth, and that the offspring shared in this advantage. Since
Weissmann's time, however, every Lamarckian feels it necessary to
suggest some method by which the altered body of the parent can
produce modifications in the germ plasms from which the young are to
spring. One of our later biologists begins to talk of some effect
comparable with wireless telegraphy or induced electricity. He
believes that organs in the adult, not necessarily by direct action,
but by action from a distance, may alter the germ. Of this, there is
no proof at present. Others have suggested that just as the ductless
glands pour into the blood chemical substances which materially affect
the growth and development of other portions of the body, so similar
enzymes, or other chemical substances, may be sent into the blood,
which subsequently bathes the germ cells of the coming generation and
produces the change. But of this, again, there is no proof. We may
believe that acquired characters are transmitted, but we certainly do
not have a very clear idea as to how it can be done.

One of the strongest objections to Darwin's idea of evolution by
natural selection of small and favorable variations, is that the
process is too inconceivably slow to account for the enormous progress
which has been made. The answer has always been that our observation
ran back so short a time that we really have no clear idea of how
rapid evolution may have been. Again, it has been answered that
transitional geological periods, in which there is much change in the
physical geography of a country, will produce more rapid evolution
than we at present are experiencing.

Hugo DeVries, of Amsterdam, believes he has found the answer to this
difficulty. Outside of his botanical garden an American species of
Evening Primrose had run wild. In looking over a number of these
plants he found, every here and there, certain peculiar members of the
species. They differed noticeably to the practiced eye from the rest
of the group. When they were planted and crossed with each other, and
the resulting seeds were again planted, the peculiarity remained
constant in all the members of the collection. Here then we have a
true variation, not large in amount, but at the same time quite
definite, and which from the first remains true. Here are the
beginnings, says DeVries, of new species. They are true from the
first; they can live among other members of the species and still come
true; they do not need isolation, at least in Wagner's geographical
sense. These forms DeVries calls mutations. It is his thought that a
species may run along uniformly for a long time when, from some cause
which he has not determined as yet, instability comes into the species
and it varies in quite a number of directions. Each of these
variations may be the starting point of a new species. DeVries
believes that he has at least half a dozen mutants of his new Evening
Primrose.

This theory of Mutation has been eagerly seized upon by many
botanists. The zoölogists have not accepted it quite so
enthusiastically. If this is the chief method by which species
transform, it seems strange that we do not find more mutations than we
do. Perhaps we do not look carefully enough; perhaps we shall find
them a little later. Just at present it seems premature to believe
that all evolution is by mutation, although quite possibly some of it
is. The main apparent advantage of mutation is that it hastens the
time in which a new species may arise.

There are certain difficulties which run back into the problem, and
which must first be reasonably solved before a clear understanding of
the idea of evolution is possible. The first of these is as to the
nature of life. What is life? The reply of the biologist will probably
be that so far as its material side is concerned, it must be answered
in terms of physics and chemistry. As to any side not material, if it
have any such side, science says that the chemist can have nothing to
say. The chemist may have an opinion of his own based on some other
ground than his chemistry, but so far as he is a chemist, he has no
opinion. The chemical side of life is being very carefully and very
fully investigated. We are certainly being brought nearer to the
borders of the living substance. We are rapidly gaining fuller
knowledge of the physical and chemical processes which constitute
life, or with which life is always associated. If we gain this
knowledge we shall be in better position to solve many of our other
problems. Even then there is a problem which preceded and which will
possibly always defy solution. How did life originate? Has it
developed out of chemical and physical activities which we know as
heat, light or electricity? If so, what were the conditions under
which it developed? If we understand the nature of life, and the
conditions under which it developed, we may be able to produce it at
will.

A few scientists may hope dimly that this will be attained. I suspect
a great majority believe it to be impossible, and that the question as
to whether life evolved upon this planet, or this planet became
infected with life through meteoric dust from some other center, will
forever remain an unsolved problem.



CHAPTER X

THE FUTURE EVOLUTION OF MAN


The disturbance of mind created by the publication of Charles Darwin's
"Origin of Species" would have amounted to nothing if the theory had
been applied to the lower animals alone. Few people would have
disputed that a cow and a buffalo had descended from the same
ancestor, or that monkeys and apes were of a common blood. The whole
theory would have been looked upon by those outside the biological
world as entirely an academic question, in which they had little
concern, and less interest. But within this century the scientist has
so persuaded the world of the unity underlying the activities of the
universe, that so soon as a principle is established men begin to run
it out to the very end. Everyone knows perfectly well that if it could
be proved that the dog and the horse had a common ancestor, still more
if it could be made apparent that the dog and the frog and fish had
sprung from the same stock, then there could be no question of what
would be the final application of the theory. Man himself could be no
exception to the law. So the battle dropped at once upon this most
interesting point, and around this center the contest has waged.

What is the origin of man? Who are his ancestors? As soon as we ask
the question there is no doubt whatever as to the answer, if we accept
the principle of evolution. Our only means of judging relationship
between animals is by the similarity of their structure. As soon as we
come to examine the other creatures even in the most cursory fashion,
there is only one group which in any close degree resembles the human
species. Our nearest relatives among living animals must undoubtedly
be the apes. Some little distance farther away stand the monkeys, and,
structurally speaking, there is more difference between a monkey and
an ape than there is between an ape and man. The gap between man and
his relatives of this group, known as the primates, is a mental, not a
physical one. While his brain and his mind have developed far beyond
theirs, the rest of his body is comparatively close to that of an ape.

Probably no one can face the possibility of his being descended from
creatures not unlike the ape, without feeling a stirring sense of
repugnance. The least aristocratic of us hesitates to name in the line
of his ancestry creatures so unlike himself as the members of this
group. It seems to us impossible that we should have descended from
creatures as lowly as they. If evolution is true, these are among our
near ancestors. Back of the group of primates lies a far less
developed set of insectivorous animals, behind them the reptiles,
behind them the fishes. When we get back this far we are less certain
but most probably the worms take up the story. So our ancestry runs
back to the very beginning, when it originated in the one-celled
animals which are also the ancestors of all the rest of the animal
world. If we are inclined to deny our ancestors in the trees, what
shall we say of our forefathers in the seas?

The question of course is not to be decided by our likes or our
dislikes. If the evolution of man is true it will not make it less
true because the process is not to our liking. It is our part, if this
be the truth, to accept it as we do any other truth. Surely those of
us who are moral of thought are not willing to disbelieve a truth
because it is unpleasant.

The newness of the idea is the chief reason for our dislike of it.
This lowliness of origin should not be distasteful to us. Nothing
about Abraham Lincoln seems to us more wonderful than that a man who
towered head and shoulders above his generation, indeed above most
generations of men, in his fineness of life, in his nobility of
purpose, in the integrity of his aims, should have been of
exceedingly humble extraction. It only adds to the glory of his later
achievements that he should have lived in a cabin, have spent his
young manhood splitting rails and running a flat-boat, and have gained
his education almost unaided from a few books and much meditation in
front of a log fire.

That the greatest military General on the Union side of the Civil war
should have been the son of a country tanner, and as a boy, not
over-shrewd in the matter of bargains, adds to the glory of his later
life. The simplicity of his childhood gives new luster to the power
with which he led the forces of a nation to victory, and then went to
a battle no less noble in his long fight for honor while suffering
from disease and approaching death. Why then should we feel that such
beginnings in the lower world are too humble for man? Why do we think
his present superiority diminished by his lowly origin? Why can we not
see that precisely the reverse is true? The more humble the level from
which he sprang the more gloriously creditable is his present
position. Instead of being ashamed of having risen from the brute, it
should be the glory of man that he has so sprung. His chief
superiority lies in the fact that while they have remained where they
are, he has so completely outdistanced them as to have placed a gap
between himself and them that seems almost impassable. Furthermore,
if man with his present glory of intellect and of moral impulse, has
sprung from a creature whose superiority to the ape lay chiefly in its
potentialities, then it does not yet appear what he shall be. We can
judge the future only by the past. Through the long ages the
development has been very slow. Through the last hundred thousand
years the development of man has been wonderfully rapid, compared with
what went before, though it seems slow enough when we look at it from
the standpoint of our historical and traditional reports. But with
this added impulse, this rapid improvement that has come with the
development of mind instead of muscle, of tooth and of claw, we have
every promise of an evolution that shall far surpass anything that has
yet come. To-day our leaders are way beyond the average of the mass.
Who shall doubt that in a not too distant to-morrow, the masses shall
be where the leaders of to-day now are. We shall not then have reached
a dead level of superiority. Our leaders will have moved on as rapidly
as have the masses, and will be as far ahead of them then as they are
now. It shall be their work to apprehend new virtues, and to work them
out in their lives. The masses, seeing the beauty of the lives of the
leaders, recognizing in those lives the revelation of the divine power
which they have apprehended, will hunger to learn of them and to lead
lives like theirs. To this process who shall set an end? The advance
is slow, as in all evolution; but anyone who wishes to do so may
easily detect the direction of the current.

The evolution of man's physical frame probably has nearly ceased.
Gradually organs that are useless to him are passing away. Slowly his
hands are becoming more delicate and refined and skilled. But his
evolution has begun to work itself out on entirely other lines. We
sometimes hear that the men of the past were the full equivalent of
the men of to-day. Scholars like to tell us that the population of
Athens was finer in quality than any population that has existed
since. We must remember that group after group of men may be expected
to specialize intellectually and fail to develop morally and
physically. Under these conditions this little branch of the human
race runs through its forced flowering and comes to an end. With the
study of history and the earnest investigation of these lives of the
past, new possibilities arise within the human family. The next race
that flowers may take longer to decay because it understands better
the weaknesses that carried away the preceding civilization. In time
there will arise a civilization that understands the past. A whole
people will some time realize that intellectual development alone will
not save it, or Athens would have lasted; that moral development
alone will not suffice, or Judæa had been permanent; that physical
development will not serve, or Sparta would stand to-day. Some day
there will arise a nation that will see to it that every intellectual
advance is accompanied by an equivalent moral and physical advance.
When this time comes we shall have a race which can survive. Are we to
be that race? The sins of man are generally the dregs of his brute
ancestry. Bestiality of life was once common enough to attract no
attention. Kings and nobles were not supposed to be clean so long as
they confined their bestial relations to those below them in rank.
Gradually men are becoming ashamed of uncleanness in life. Some day
there will be no difference so far as purity of life is concerned,
between the two who present themselves at the altar asking the
blessing of God on their union.

If anyone doubts that English speaking people are becoming cleaner of
life he needs only to consult the literature of the past. No one
dreams of finding fault with Chaucer because his stories related in
the company of men and women often would not bear such telling to-day.
Shakespeare, with all his wonderful genius, needs expurgating if one
would read him aloud comfortably to a mixed audience. And these are
the shining stars. When we drop below them, the literature of their
time becomes nearly impossible to read. Fielding and Smollett and
Stern helped to build up the English novel, but the stories they tell
speak of the grossness of their time in language that is unmistakable.
We are by no means clean to-day. A fair proportion of our novels leave
much to be desired. The stage is the scene of much we could wish to
see cleaner. Above all this grossness there towers a sweetness and
beauty of thought, and an earnestness of purpose, a sincerity of
effort, which makes the present time fuller of moral purpose, fuller
of the desire to be clean and to help others to be clean, than graced
any previous period in the history of either England or America.

Under the change from country to city life man has suffered. Here too
evolution is necessary. City life tells hard on the second generation
and nearly destroys the third; but we have come to understand the
difficulty and are fast remedying it. It is more than possible that
the next generation will see such changes in the life of the worker in
the great center, as shall effectively stop the physical deterioration
that has come to the city dweller. God grant that modern civilization
has had teaching enough and learned its lesson well enough. God grant
further that we may give over slaughtering our most ambitious and
vigorous young men in battle to settle questions which battle can
never settle. God grant that we have come to a turning of the ways
where the life of men, women and children, no matter how humble their
station, shall stand higher in value than the profits of any
commercial venture. God grant that we will soon be firm enough to
declare that a business which can only live by sacrificing the health
and strength of the workers must be counted an unprofitable business,
and be allowed to cease. God grant finally that the American people
may learn from the past to guard against a like fate in the future;
that here may be the people whose strength, intelligence and
uprightness shall lead the world; not for the sake of exceeding the
world, but with the high mission of setting to the world an example of
what can come to a vigorous, free and God-fearing people.

In the early history of the evolution of man the struggle almost
always concerns the individual. Gradually the family comes to be the
fuller unit. Only that is success which leads to the success of this
higher group. After a time the family broadens to the tribe, and then
the tribe to the nation. The evolution of social institutions is at
present going on at an enormously rapid rate. Throughout the civilized
world democracy is coming to its own. Even where the form of monarchy
still prevails, the subjects of the monarch are having more and more
rights. The people of England are surely as free as are the people of
the United States. Increasingly all forms of government will secure
for all their subjects, no matter what their station in life, a fair
share of the general prosperity. In this field, human evolution is
perhaps more rapid than in any other.

Any individual human being is a network of traits and peculiarities.
He has all the ordinary attributes of humanity, but to the whole
complex he gives an individual peculiarity which is totally his own.
Where did he get his qualities? In the earlier times the fairies were
supposed to have blessed him or cursed him in his cradle. A later age
saw in the stars the rulers of man's destiny. He was jovial, or
saturnine, or martial, depending on the planet which was in the
ascendant at the time of his birth. Now we know "it is not in our
stars but in ourselves that we are underlings." Everything a man is
comes to him from within or from without; from nature or from nurture;
from his heredity or from his environment. From our ancestors we get
all the possibilities of our lives. To a certain extent we are slaves
to our heredity, but not by any means to any such extent as to make us
hopeless, unless our heredity is miserably bad. To the great mass of
us come larger potentialities than we ever develop, and such
possibilities of degradation as, fortunately, few of us ever reach.
Within an enormously wide range, man is the architect of his own
fortune. Only such traits develop as find a stimulus in the
environment. Accordingly, a very large proportion of the development a
man may achieve depends upon the circumstances under which he is
placed, or, what is far more to the point, in which he may place
himself. Man is not the blind sport of a relentless destiny. It is his
to choose his environment; it is his to modify his environment when he
cannot leave it. To an extent which no other animal has ever
approached, man is the arbiter of his own destiny. A hypothetical ass
may stand helpless between two equidistant bales of hay, but no human
being is ever so helpless a sport of his environment. As it is, he may
drift or he may rove as he pleases. To one man the current may be
stronger than to another. There may be now and then a child so
feeble-minded as to be unable to decide the course of its own life. It
will not be long before society will see to it that such a life leaves
behind it no strain cursed with its fatal weakness. In this effort to
advance, man has all the advantage that comes from concentrated social
effort. No man may live to himself. To every man in our community who
desires it, a helping hand will be stretched. Often a hand will be
stretched to him and he will be steadied whether he will or not,
until his own will reforms itself and gains the mastery.

Inasmuch as all that is in man comes from his environment or from his
heredity, the only way in which the race of men can be advanced is by
improving their environment or by bettering their heredity. The first
of these is the province of the sociologist; the second that of the
eugenist. The sociologist has for some time been giving his careful
attention to the improvement of the environment. In every large city,
a man must build for himself a house fit to live in, if he build it at
all. Whether he erects it for himself or for another makes no
difference. Society will no longer allow him to build a home which is
a detriment to the one who lives in it. Not only must he make himself
a decent home but he must keep it in decent condition. The community
will not allow him to endanger his own health, or that of his
neighbor, by an insufficient method of attending to his garbage, or by
a lack of ordinary cleanliness. If he will not clean his premises
himself, the law sees to it that they are cleaned for him. Already we
are beginning to understand that no man has a right to employ another
man or woman or child at wages which are not sufficient to maintain
the one thus employed. The wages of many people are exceedingly
meager, notably those of women and children. He can read but ill the
signs of the times who does not foresee an early end to the exploiting
of the labor of these helpless creatures. Humanity has determined
firmly that these things must pass, that the young child must not
labor long or hard, that a woman must not be taxed beyond her
strength. Already in England there is a partially successful movement
which will doubtless spread to this country to provide that a woman be
granted a little time before and after the birth of her child during
which she shall not be allowed to suffer because her power to earn a
wage is temporarily gone. These things cannot fail in the long run to
strengthen the people. They strengthen chiefly the present generation.
The blight of the fact that acquired characters cannot be transmitted,
meets us here. This improved environment can only slowly, if at all,
improve the race, and every effort made in this direction must be
repeated with each generation.

Under such circumstances is it to be wondered at that the eugenist is
hoping to raise the strain? Any improvement he can bring about is not
only valuable for the generation in which it comes but is carried on
into the generations which follow. This is the hope that strengthens
and sustains him in his effort. The science of eugenics is so new, so
little is surely known concerning the transmission of human
characters, that no one is able as yet wisely to say what course is
to be pursued in improving the race. But the problem is so interesting
and its outcome so overwhelmingly important that men will never cease
striving to know, and may, before many years, begin wisely to guide us
in our efforts to provide a finer stock.

Heretofore our efforts at improving the strain have been confined to
cattle, chickens and plants. An almost unalterable repugnance rises as
soon as we speak of improving the human strain. Visions, if not
stories, start up at once, of experimental matings of human beings,
and of all other unspeakable abominations which no decent man expects
to happen or even wishes to attempt. If there is one thing in human
society the value of which has been demonstrated through the unending
ages, it is the monogamic marriage. All ideal workers must point to
the life-long union of a strong, vigorous, clean-minded and
clean-lived man with a similarly fine, strong, clean-minded and
clean-lived woman. Such an ideal may be slow in its attainment, but he
aims too low who aims to secure anything less than this. The long
struggle out of bestiality into pure monogamy has been so slow, so
gradual, so noble in its attainments, and is still so far from
perfection, that it would be an inconceivably stupid blunder to let go
a single point that has been gained. Whether divorce shall be allowed
to remedy a mistake may be a matter of dispute, but at best it is a
bad remedy for a mistake that should never have been made. No ideal
society could ever consider divorce as any permanent portion of its
activities. Children are not like cattle. It is not simply a question
of their being brought into the world sound and strong. Their long
infancy which in the biological as well as in the legal sense, lasts
until they are grown up, should be spent in surroundings which can
minister, by example and precept, to moral and intellectual
development. Surely no such end can possibly be attained when man and
woman mate lightly, to part quickly.

At first sight it would seem a wise thing to require health
certificates for those who would be married. I doubt not the Chicago
Bishop who declined to marry his parishioners except under such
conditions, will exert a beneficial effect upon the country by the
attention he thus attracts to the subject. It would be a bad day for
the city if all the clergy and all the other authorities who are
authorized to solemnize marriage should take this step. We have not
yet arrived at such a stage of development that a marriage certificate
is essential to mating, and a restriction of this sort would simply
mean that there could be no legitimate union except of those in strong
health. To the burden of ill health would be added the still worse
handicap of an illegitimate parentage, with all its bitter train of
scorn and shame. Accordingly, it must be possible before the law for
those who are not thoroughly vigorous to marry. But, year by year, we
may come nearer accomplishing a finer mating by the aims and purposes
we foster in the growing generation. Marriages will never be worth
while when they are not freely entered into by the contracting
parties. Choice must be free and unrestricted if it is to last for
life; but this does not mean that it must be unguarded. It would be
bitter folly for parents to leave to their children, without attempt
to influence or restrain, the making of their marriages. The mating of
our children must be inspired, not directed.

There is one taint from which society has the right and the duty of
freeing itself, so far as in its power lies. This is the taint of
feeble-mindedness. Of all the calamities that can befall a human
being, feeble-mindedness is, perhaps, the worst. From most misfortunes
it is possible to recover; with most of the rest one may exist without
detriment to the race. To be feeble-minded simply means to hark back
to the level of our animal ancestors, without regaining their power to
guide life. The animal is provided with a bundle of instincts which
tell him what to do in all the ordinary emergencies of life. The
human species, in its development, has lost a large portion of its
instincts, and has gained, instead, the power of intelligent choice
and the ability to learn by imitation. When these drop away, man
without his instincts or his intelligence is more helpless than the
brute. Students of sociology are making clear to us that a large
portion of the criminality of the world, much of the looseness of
life, and a large part of the alcoholic excesses are due to this taint
of feeble-mindedness. Recent investigations have made it clear that
one feeble-minded family in a community may, in the course of years,
poison the life of an entire state. The Jukes family in New York, the
Kallikak family in New Jersey, have shown the awful possibilities of
descent from a single feeble-minded ancestor. Prisons, almshouses, and
houses of shame owe their population in no small degree to this bitter
curse. It will not be long before society will learn to protect itself
against such poisoning of the human stock. Nothing is more clear to
the investigator of this subject than that the one overwhelming cause
for feeble-mindedness is feeble-mindedness in the parentage.

There is one type of mental weakling, known as the Mongolian idiot,
which may arise right out of the heart of an apparently sound family.
But the number of these is comparatively small. The number of
feeble-minded, who are feeble-minded because of their heredity, is
dishearteningly and astonishingly large. Every attempt to examine
large numbers of school children shows a sickening proportion of those
who are distinctly feeble. Every little community seems to have its
boy or girl who is what is known as silly. Such people rarely live
long lives without leaving behind them feeble-minded children, no
small proportion of whom are likely to be illegitimate. Against this
fouling of the stream at its source, society must protect itself.
Legislators revolt at the somewhat inhuman but certainly safe method
of surgically preventing the possibility of the feeble-minded becoming
parents. It would be more creditable and just as effective if society
would take upon itself the tremendously expensive task of caring for
all its feeble-minded in institutions during their entire life. The
cost would be large for a generation, but would rapidly diminish and
eventually become small. It certainly would be the humane way. These
people in good institutions are by no means unhappy. Within the limit
of their capacities they can do many things. Wise management usually
will secure from them labor enough of wholesome and simple kind nearly
to pay for their own support. Nothing could be better for them than to
till the soil, care for the cattle, tend the chickens, and, in this
way, provide very largely the materials on which they are fed. How
this problem shall work out, time only can decide. With it once worked
out, there is no doubt that the level of humanity will be distinctly
raised. No other one feature in the program of eugenics seems more
absolutely hopeful than this.

In several of the states of the Union it has recently become the
practice to remove the possibilities of parenthood from certain
classes of criminals. The purpose of this is clear and benevolent.
Society has a right to prevent the oncoming of new generations of
foreordained criminals. Underlying the practice is the theory that the
children of criminals are born criminals. It is far from likely that
this is the case. Criminality may be due to a wide range of causes. If
the criminal is one of those actual born degenerates whose whole
mental and physical make-up is so defective that nothing but
criminality can be expected of him, then we have a case in which it is
clear that society may, and should, remove the possibility of having
more generations of the same kind. Probably only a moderate proportion
of the criminals in our jails and penitentiaries belong to this class.
Doubtless a distinct majority are criminals more through environment
than through heredity. Born of average ability, or more, these people
have been criminals simply because they were reared among criminals,
because their surroundings were such as to lead them away from habits
of industry, while they must live. These people were not bolstered by
society, or the church, into a life of self-respect and self-help.
Under these circumstances they fell into evil ways. There is nothing
defective in their mental or physical make-up, that need appear in
their children. If these children are removed from contact with the
criminal class they stand every chance of being as vigorous, as
intelligent, as upright as the average of the community.

At the recent Eugenics Congress in London one of the speakers
expressed a preference for the son of a husky burglar over the son of
a tuberculous bishop. This is doubtless quite correct, but why should
the bishop be tuberculous? The truth of the matter is, the reverse is
more likely to be the case. Personally, I should prefer to be the
offspring of a husky bishop. In dealing with criminals, then, with a
view to cutting off their posterity, we must be careful to understand
whether we are dealing with a hereditary or an acquired criminality.
If there is a genuine hereditary criminal taint, society is right in
freeing itself of it. If it is acquired criminality, then it is not
transmissible, and the offspring, if placed in a good environment, are
likely to be good citizens. All of which means that, until we are
clearly sure of what constitutes a hereditary criminal trait, we
should move very slowly in the matter of mutilating criminals.

What steps may the eugenist, with his present limited knowledge,
clearly, hopefully and confidently take to improve the future of the
human species? There is one avenue open to us in this matter in which
we can hardly go wrong. Even our mistakes can work little harm, and
every well-done piece of work in this field will be a blessing to the
race. This step lies in inculcating in our boys and girls high ideals
of parenthood. This is more effective than legal prohibition of
certain forms of marriage which cannot prevent matings, and adds the
curse of illegitimacy to the other handicaps of the children of such
unions. The first step in this process has already been reasonably
well accomplished. Both our boys and our girls are in love with
health. A good husband and a good wife should be healthy and vigorous.
This does not mean that we expect a boy or girl who is looking forward
to marriage to sit down and ask himself deliberately about the health
of the person with whom he would mate. We must fill our children with
the love of outdoor life, with the love of exercise. This will foster
in them an admiration for people who are vigorous of body and alert of
mind. It ought to become practically impossible for a hearty and
vigorous boy to fall in love with a helpless and anæmic girl. It
should be equally impossible for a hale and active girl to admire a
man who was her inferior in either vigor or alertness. The modern
taste for outdoor life has largely brought this to pass among such of
our people as have leisure enough to indulge in vigorous sport. Among
the crowded dwellers in the closer sections of the city such life has
been so nearly impossible that no ideal of vigorous manhood or of
radiant womanhood has had a chance to grow up. With the oncoming of
the parks and play-grounds, all of this, we may hope, will change.
Health and vigor will be no less attainable and hence no less adorable
in the city than in the country. Rich and poor alike will be attracted
by rosy cheeks and an elastic gait.

Our aim, however, should not cease with a vigorous body. We must teach
our young men and young women the glory of a well disciplined mind.
This should seem quite as admirable to them as a vigorous body. To
them, straight thought ought to be as lovable as a firm and supple
body. In this matter our young people are less exacting. The ordinary
conversation of people gathered together for social purposes is not
particularly intellectual, and any attempt to make it so at present
seems priggish. With a broader education, will come keener demand for
intelligence. We may hope the time is not too far distant when a
question of governmental policy, a new book or play, or a new
discovery in science will stimulate as much conversational zest as now
seems to be gotten from a pack of cards.

A third feature of the ideals which should be instilled into the minds
of our children is the moral phase. There seems little doubt that this
is on the way. We must not mistake an evident laxness of religious
observance as being synonomous with moral looseness. The revelations
which our recent periodicals have brought us concerning the habits of
business men, of politicians, and of society, have left on many minds
the impression that this is distinctly an age of decadence. Exactly
the reverse is the truth. This is the age of intense sensitiveness to
wrong. In almost no particular is it worse than any previous age in
the history of our country. We openly discuss things which we left
untouched a little while ago. We insistently demand that business
practices to which nobody particularly objected a dozen years ago must
now certainly cease. All of this has produced an erroneous impression
that the times are out of joint. But the dust and dirt in the air is
the unavoidable accompaniment of house cleaning. When doubtful
practices simply have publicity many are awakened to the sense of
their duty to society. Persons who, of themselves, might be willing to
live low and godless lives, dare not do so in the face of society when
our social ideals are finer. I believe there is the utmost hope that
within two generations our young men and young women will scorn
meannesses which we are accepting with entire complacency.

A close acquaintance with thousands of young men and young women
running through an experience of twenty-five years has taught me to
believe that our young people of to-day are altogether cleaner of
mind, of tongue, and of life than were their parents. There is freer,
franker discussion of many things that their parents would scarcely
have dared mention, yet I feel sure the moral tone is distinctly
higher. I look with entire hopefulness to an early season when the
young man who asks a woman to share her life with him will be met with
the entirely proper question, "Have you kept your life clean for this
event?" I believe that unless the answer can be in the affirmative the
young woman will not be able to have admiration enough for the young
man to cover uncleanness in his life.

There is one temporary phase of present life which seems discouraging.
The increase in the cost of living, and still more rapid increase in
the standard of living is shifting too late in life the age at which
our young people marry. The result is that one of two things is likely
to happen; either a large number of people are likely not to marry at
all, or the romantic time of life is passed before the event occurs
which it is intended to bless. A young man and young woman who are in
this time of life can deny themselves for each other, can struggle and
plan together, can hope and trust together to an extent that can never
be the case if marriage is delayed beyond the romantic years.

The best foundation possible for a life of happiness is vigor, ability
and good character. For the lack of none of these can wealth properly
atone.

There is an apparent tendency to waken to the situation. I hope it
will come soon enough for our young men and young women to get past a
desire for such establishments in life as their parents already have.
With this difficulty removed, with our widespread education, with the
constant diffusion of both information and ideals from our periodical
press I have every hope that the evolution of a new, a finer, and more
vigorous race, will come with a rapidity which nothing that the past
has done would lead us to expect.



CHAPTER XI

SCIENCE AND THE BOOK


We of the twentieth century have an overwhelming desire to be up to
the times. Nothing but the latest news on any subject will completely
satisfy. We are more anxious for late information than for accurate
information. We have an almost unconquerable feeling that if it is
late it must be accurate. All of us are sensitive to being thought
behind the times. We feel that no stigma can be more invidious in the
intellectual world than the stigma of being out of date. This pervades
the masses quite as strongly as it does the more cultured classes.
Under these conditions everybody wants to know the latest theory that
science has to offer concerning anything that can be brought within
the range of their interests. As a result everybody would like to know
about evolution, were it not for the fact that a great mass of people
have been brought to believe that there is something inherently
irreligious in the idea. Our people have a saving sense of the value
of religion. Denominational control may set lightly upon them.
Certain long revered doctrines may have little practical influence
upon them. Yet inherently they all believe in religion, and most of
them believe themselves to be religious, as indeed they really are.

It is a most wholesome tendency which leads us to esteem religion as
the main interest in life. We must feel a sense of shame when we
consciously permit the influences, which most favorably mold our
character, to weaken their hold upon our lives. Certainly in our time
religion is the essential agent by which character is molded. Any of
us would be foolishly short-sighted were he willing to weaken the hold
of religion upon his life for the sake of a scientific theory, the
truth or falsity of which could have but little practical bearing upon
his conduct. We must hold to religion at all hazards. We may, when
circumstances so suggest, change our denominational allegiance. We may
and often do interpret our faith quite at variance with the
ecclesiastical body with which we are connected. We may constantly
modify and develop our beliefs. But it is a pitiful life which has
lost the staying and strengthening influence of religion. I believe
this conviction is deep-rooted in the minds of our people and that it
deserves the place it holds.

To a mind thus essentially religious the announcements of science
often come as a shock. They seem to run counter to our deepest
convictions. It seems impossible to us that both can be true.
Sometimes the more we debate the questions the more contradictory they
seem to become. Every good mind needs unity in itself. No clear
thinker can be quite content when two distinct departments of thought
are at sharp variance in his mind. He may pursue one of two courses.
He may hold to one view with conviction and earnestness and look upon
the other as essentially false. To many religious people all science
that runs counter to their convictions is necessarily false. They
label it pseudo-science and pass it by. If the word pseudo-science is
unknown to them, they stigmatize it as rationalistic, or still worse
as materialistic and let it go at that.

The other course is to have faith both in religion and in science.

Such a fair-minded man must ask himself, what is the truth in the
matter? If the scientific fact is true it is to be believed. It may
run counter to what we have believed before. It may seem at first
entirely incredible. But when once he becomes convinced of its truth
the clear thinker must not only accept it, but must accept all
legitimate deductions from it. If it seems true to us we must believe
it. Absolute demonstrable truth, except in the simplest of matters is
almost unattainable. The best we can ordinarily get is a close
approach to certainty, and with this we must be content. In many
matters, indeed in most matters, we must trust the judgment of others
who are better trained in a particular line of thought.

As to the truth of geology we are certainly wise to accept for the
present the facts and principles commonly accepted by competent
geologists. In biology, we should respect the concurrent opinion of
important biologists. We must not assume that a few biologists who
think as we do are right against the biological world, or that a few
geologists who think as we do are right against the geological world.
For theology, we had better go to the educated theologian. But when it
comes to reconciling two of these and to catching the inherent
correspondence between them, it is often likely that each of these
groups of men is unable to see clearly the view-point of the other.
Here lies our freedom. Here we must either think for ourselves or
think with those wiser than ourselves whose opinions seem to us to
ring true and to focus for us our wavering and uncertain thought.

Among students of animals and plants there is no longer any question
as to the truth of evolution. That the animals of the present are the
altered animals of the past, that the plants of to-day are the
modified plants of yesterday, that civilized man of to-day is the
savage of yesterday and the tree-dweller of the day before, is no
longer debatable to the great mass of biologists. To older men
hampered by the convictions of an earlier age this dictum of modern
science may still be a little uncertain.

The working biologists of the world have no doubt. They differ
radically as to what brought about this change, they dispute
vigorously as to the rate of change, but as to the fact of the change
there is no difference of opinion. Under these conditions the thinking
man is out of joint with the times when he sets himself against the
idea of evolution. He may be so immersed in other lines as to be
indifferent to the problem; but when he is hostile to it, he marks
himself as clearly against his day. Many have been against their day
and have been right. Very great men have often been against the
opinions of their times and have come to be leaders of the world's
later thought. But ordinary men in ordinary times who think
differently on a special subject from the specialists of the times are
not very likely to be right. It is safe for most of us to accept as
true an opinion on which specialists on that subject agree. It seems
clear to me then that the thinking man to-day has in the matter of
evolution a double duty. He must become reasonably acquainted with the
theory that so largely affects all present knowledge, and he must
wrestle with the theory until it no longer hinders the hold of
religion upon his life. He may be perfectly sure that he does not
clearly understand both, but he must get them into reasonable
concordance before he can be quite at peace.

Truth is true no matter how it is acquired. There can be no doubt as
to the essential truth of religion: its fruits proclaim its worth.
There can be no doubt as to the essential truth of evolution; the
clarity it has brought into the sciences is the evidence of the value
of the conception. That it will persist in its present form, that it
will be unchanged by later additions to our knowledge is of course
unthinkable. It may be incomplete, it may be undeveloped, but so far
as it goes it contains the truth. Under these conditions, how can we
bring peace into our own mind? These two important provinces seem so
often to be at variance. The difficulty may lie in one of two places.
In the first place, each truth may be stated in terms so peculiar to
its own subject as to convey no meaning to the student of the other
branch. There is a second, and more harassing possibility. The same
words may be used by students in each branch but each side may put a
different significance into the terms. Then each believes he
understands the other, when he really does not.

Our theology is man's interpretation of God's revelations of Himself
as recorded in the Bible. Our science is man's interpretation of God's
revelation of Himself in nature. Each is God's revelation, and so far
as we have understood it, that revelation is of the utmost importance
in our lives. Each has all the inherent short-comings of man's
interpretation. Each has all the difficulties necessarily found in any
stage of a developing understanding. We may be sure if we could
thoroughly understand God's revelation of Himself as recorded in the
Bible and his revelation of Himself as recorded in the rocks and the
tissues of animals as well as in the body and mind of man to-day,
there would be no difficulty. When we understand both completely, as
perhaps we never shall, there will be no contradictions of any kind
between them. Even now if we are firmly convinced that truth must be
in both, there will be little difficulty in reaching a workable unity
which will satisfy the present needs of the human mind and will not be
so crystallized as to prevent a future growth. If, however, we hope to
find a unity between a belief in evolution and a belief in the
inspiration and value of the Bible, we must accept both of these in
the terms of to-day. To reconcile a twentieth century statement of
science with an eighteenth century statement of theology would be as
absurd as it would be to reconcile a statement of twentieth century
theology with eighteenth century science. Each century must restate
its truths in terms of its own time. The truths may be at bottom the
same through many centuries but to be clearly intelligible in any
century they must be couched in the terminology of the age.

It seems to me if we are to understand, in conformity with the thought
of the age, any particular book in the Bible, there are three steps
through which we must pass. We must first ask ourselves the kind of
people to whom the book was originally written. We must know their
habits of life and of thought. Until this is clear in our minds the
book can have little significance. Having built up as nearly as may be
the life and thought of the time, we must next decide what is the
inherent truth taught to the people of that time by the book under
consideration. Much that is written must be simply the setting in
which alone that truth could reach them. This extraneous detail gives
vigor and color to the message but is not the message itself. The last
step and the hardest one to take, the one that to some minds seems
almost irreverent, is to decide the form that message must take to-day
to convey to our minds the same truth which the original message
conveyed to the people of its time. In so far as we succeed in taking
these three steps, we shall get the true message which this book
holds for us to-day.

When Paul in his first burning letter told the Corinthian congregation
that their women should be silent in their churches, he is not, it
seems to me, giving a message which in those terms applies to the
world to-day. If a woman has anything that is worth saying she has a
perfect right to say it in church. In any denomination in which
religious observance is not ecclesiastically formal she will be
allowed that privilege. By an interesting peculiarity of mind on our
part she may be permitted to do so upon Wednesday evenings, when our
early prejudice still prevents her speaking on Sunday. What is the
truth of the teaching of Paul in this matter? The Christians of
Corinthian times had already begun to suffer from persecution. They
were already despised and distrusted. Men had come to speak ill of
them. Paul's injunction concerning the silence of women in churches
was simply an injunction against their doing those things which in the
thought and habit of those times were associated generally with
looseness of character. Fine Corinthian women did not speak in public.
A woman who would consent to speak before a group of men of Corinth of
that day would by that fact have proclaimed herself a woman of loose
morals. Paul's injunction is that, in this desperate struggle
Christian women should do nothing which could possibly bring them into
disrepute. The lives of Christians must be above suspicion. This
message is certainly as true to-day as it was in the time of Paul and
Corinth. Whether or not a woman speaks in church to-day has no bearing
whatever upon the question. The question is how she speaks and what
she says. If her life gives force to her message and her message
contains God's truth she is entirely free to speak.

In similar fashion we have changed most beautifully the message which
we have come to love, as the Mizpah message: "The Lord watch between
thee and me while we are absent one from the other." We have
absolutely transformed and glorified the message. It was once the
calling down of the wrath of Jehovah upon one or other of two herdsmen
if either of them should fail to comply with the agreement to remain
within his own boundary. These men whose herdsmen were constantly
stealing each other's cattle agreed to separate because they could not
live in unity. They set up a heap of unhewn stone, and called upon God
to guard and to see that neither of them passed beyond the boundary of
the other. What was once a threat between warring herdsmen has become
a binding link between Christian brothers. No longer do we call upon
the Lord to guard in our absence lest our enemy encroach upon our
domain. Now we call upon him to bind our hearts together so that
neither time nor circumstance can bring division between us. The
menace of a herdsman's wrath has become one of the tenderest messages
of Christian love.

In the light of the principles stated above, what is the essential
truth that lies back of the earliest chapters of Genesis? First, that
there is one God. Slowly it had been borne in upon the Hebrew mind as
upon no other tribe in the world that the Lord God is one God. Nearly
all the world besides believed in many gods. Each nation had a God
peculiarly its own, each city had a minor god caring for it
particularly. There were gods of the woods, gods of the oceans, gods
of the streams. Gods and goddesses were everywhere. To this people
wandering through the terrible monotony of the sandy desert, the
"Garden of Allah," there came the inspired comprehension of the
eternal oneness of Almighty God. First, he was to most of them the God
of the Hebrew, stronger than the gods of the nations. After a while
under the teaching of prophet after prophet there finally came to the
entire nation the exalted conception that God is one and there is no
other God. This is one of the imperishable revelations of all time.
Beside this, all suggestions of fifth or sixth day, of hours or of
ages are absolutely insignificant. These are but the clothing of the
idea which makes it acceptable to its time. This clothing must change
with every age if it would reach thoroughly the minds of the age.
Underneath and forever lies the glorious truth that the Lord God is
one God.

The second truth which seems to me to underlie this magnificent
parable of creation is the truth that this great God has created the
universe and that he cares for his people. Gods before had been
objects of terror. Gods before had lived lives such as the people
themselves would not have respected among their companions. Gods
before were to be shunned. If one could but escape the attention of
the gods it was his greatest good fortune. Now we have the conception
of an all-knowing, ever-present God to whom his people are dear. The
terms in which it was stated in those days matter but little. To
modern psychologists even the idea that people are dear to God seems
speaking too humanly. Yet the truth involved must come in terms that
the people of to-day understand. We can best comprehend God if we
think of Him as loving and chastening, even though down in our hearts
we know that these terms are not high enough, are too human to apply
to an Eternal God. But we know no better and they tell us the truth
even though the terms may in time pass completely away.

Last of all and perhaps most characteristic of the Hebrew people is
the great lesson that this Eternal God, who created the universe and
cares for his people, demands righteousness of his people. To the
nations round about religion was not a matter of righteousness. For
them religion had nothing to do with morality. Thieves might have gods
favorable to them quite as well as righteous men. The worship of Diana
of the Ephesians or of Astarte in the groves of the Asia Minor coast
could be so unspeakably licentious and vile as not to admit of
description to-day. Yet this was all religion. To the Hebrew came the
inspired, exalted conception of a God who demanded righteousness of
his people. Beside this wonderful revelation to the human mind details
of serpents, and of apples, of names of men and of women, of gardens
and of swords are absolutely but the transitory clothing. This brought
them to the minds of the times. The value of the form is evidenced by
the fact that it brought the conception. But we must not lose the
glory of the conception in an over regard for the clothing in which
the idea came.

Does this mean that Genesis has served its purpose and is to-day to be
conceived of as a beautiful relic of the past, to be reverently
enshrined but not seriously accepted? Far from it. The glory of the
Genesis story lies in its wonderful power to grow. It strengthened
the minds of a persecuted tribe wandering in the desert who finally
settled in a small and barren country. It brought the truth to them so
clearly that they have persuaded much of the world of that truth and
bid fair to persuade the rest. The story has grown with the mind of
man. As it served the Hebrew in his time it has grown to serve others
to this day. Each generation has read the story in the light of its
own times and each generation will continue to read the story in the
light of its advancing knowledge. The only part of the story that can
be affected is the clothing, the inherent truth remains forever.
Furthermore, the story which persuaded the childhood of race is the
story which will persuade the childhood of to-day. In no other form
could the great truth of the Bible be brought to our children as well
as in the form of these early chapters. In early life our children
will accept these stories as literally as the ancient Hebrew accepted
them. As they grow in knowledge, unconsciously and without jar, if we
do not jar them, our children will read into the story what God has
taught them in the world outside. The shock which came to their elders
need never come to them. It is our fault if our children are disturbed
by the conflict between religion and science which disturbed us. There
is no difference between God's revelation of Himself, as we have it in
the Bible, and God's revelation of Himself in nature. The better we
know the Bible and the better we know nature the clearer this will be
to us.

Perhaps the most severe shock that has come to the mind of religious
man from the teachings of science has been the at first almost
unsupportable idea that man is the descendant of creatures of which
the ape is to-day the nearest representative. He had learned from
Genesis the altogether adorable conception that he was made in the
image of his Maker. It lifted him; it strengthened him; it gave him
more power to struggle. He might know that he had marred that likeness
by wrong-doing, he might understand that the fullness of the glory of
God's image could not shine through his own face. Yet he believed that
he was, in spite of all his imperfections, made in the image of his
Maker. Now comes this horrible linkage with a miserable brute to
either shock and confound him or to degrade him. We can easily
imagine, some of us have bitterly experienced, the shock of this
changed conception. But it was only because we mistook the clothing
for the truth in both cases. We read science in its own terms; we read
Genesis in its own terms. They did not use the same language and they
jarred us to the very soul. Slowly, however, we are coming out of the
darkness of that battle; slowly the glorious light of the beautiful
truth is breaking into our minds and our hearts.

Michael Angelo painted a wonderful picture of "The Judgment." Here,
seated upon a throne, which after all is only a magnificent chair,
sits a venerable figure of what is really but a nobly-proportioned
man, to whom the nations come for their final reward. He separates the
righteous from those who must forever be sundered from their God. Seen
through the distant past it still remains a majestic picture; but no
painter would think of repeating its conception to-day.

Quite in the modern spirit is the beautiful lunette which John Sargent
placed in the Boston Library, above his well known frieze of "The
Prophets." It represents "Jehovah confounding the gods of the
nations." The naked figure of suppliant Israel stands before an altar
of unhewn stones, on which burns the sacrifice. The smoke ascends to
Heaven. On one side stands the mighty figure of Assyria with uplifted
mace ready to strike its awful blow upon the shoulders of helpless
Israel. On the other side the lithe, subtle form of Egypt, clasping
the knout, watches its chance to bring its treacherous thong upon the
helpless shoulders of suffering Israel. But Jehovah may not appear,
man may not look on God and live. Jehovah is seen as a glory behind
the cloud of smoke shrouded by winged cherubim. From one side of the
cloud comes a mighty hand meeting with power the force of Assyria.
From the other side, a lithe and sinewy hand thwarts the subtlety of
Egypt. But Jehovah is behind the cloud.

Again we understand that we are made in the image of our Maker. Again
we understand the power of the uplift of this idea. From the conflict
it has emerged in new and glorified form. Hath a God eyes that he may
see? Hath a God ears that he may hear? Hath a God hands that he may
work? These we know to be but human forms of speaking. Eyes, ears, and
hands we may owe to the brute from whom we have sprung; in our eyes
and ears and hands we show the relationship we bear to them. These are
not the image of God. God is a deeper, a finer, a nobler something
than hands, than ears and eyes. The image of God lies within
ourselves: the image of God is that which makes us what we are. In
every noble purpose, in every earnest endeavor to uplift ourselves or
our fellowman, in every thought that turns us from the evil of a
repented past, in every desire with which our hearts yearn to
strengthen, support and sustain our friends and even our enemies,
shines forth the image of Almighty God. This it is that links us with
the Eternal: this it is that makes it worth while that we should be
Eternal. Besides this what are hands and ears and eyes? We are made,
all in us that is noblest and highest, in the image of our Maker.

A word in closing. The time is ripe for a broader conception of
theology and of science on the part of those who are not trained to be
specialists in either. We are becoming more and more inherently
religious. We are becoming more and more enamored of the truth in all
its forms. The times are ripe for us to cease the struggle and to
strive for peace. So long as men insist that the important things in
faith are the things on which men differ there will be eternal strife.
So soon as men endeavor to find the common ground between them and
each tries to state his belief in forms acceptable to himself but
involving no hostility to his neighbor, we shall be working for peace.

Some of our finest men of to-day are being trained in modern science
and in modern theology. There is no scorn in their minds for early
science or for early theology. Each served its age, and each taught
its truth. But its truth must be restated in terms of to-day. The old
creeds will always be loved. The old creeds will always hold our
reverence and allegiance. But each age must be at liberty to interpret
these creeds in the terms in which that age best understands truth.
Each age must be at liberty "to restate the doctrines of the past in
accordance with the newness of the age and with the ancient verity of
truth." How feeble my own attempt is in this matter, I quite
understand; I am still a child of the struggle. It has all come in my
lifetime and I have seen and felt not a little of the bitterness of
it. I believe the time is ripe for a definite peace. I believe our
children, if we do not hamper them, will never know the struggle we
have had. In every great institution throughout this broad land men of
earnest mind and noble soul are teaching the truth as God gives it to
them to know the truth. Let us not hesitate to entrust our children to
their hands. To us they may seem to be teachers of discord but they
are not speaking in terms that we understand. They are using the
language of a new age. Underneath their teaching lies the everlasting
truth. Out of their teaching will come everlasting life. Let us trust
God in the world. Let us believe that in this age he is teaching men's
lips and dwelling in men's hearts. Only so can we give to our children
the best their times can give them. If we insist in holding these men
back to our conception we but deny them the privilege of moving with
God's great procession. We make them laggards when they should be in
the front ranks, their faces lighted by a nearer and clearer vision of
Almighty truth.



INDEX

    A

    Acquired characters not inherited, 52.

    Adaptation and purpose, 89.

    Adaptation for the individual, 87.

    Adaptation for the species, 125.

    Advanced teaching, 291.

    Agassiz and evolution, 19.

    Age of the earth, 156.

    Allantois of chick, 206.

    American Museum of Natural History, 221.

    Anaxagoras and evolution, 9.

    Anaximander and evolution, 8.

    Ancestry of man, 186.

    Andes rising out of Pacific, 32.

    Aquinas, Thomas, and evolution, 12.

    Archæopteryx, 181.

    Aristotle and evolution, 9.

    Armadillo and glyptodon, 29.

    Artificial flavors, 161.

    Artificial proteids, 161.

    Artificial sugars, 161.

    Ascent of man, 189.

    Asexual reproduction, 194.

    Augustine, Saint, and evolution, 11.

    Australian mammals, 186.


    B

    Bank swallow's nest, 146.

    Barnacles studies by Darwin, 34.

    Beagle and Darwin's voyage, 25.

    Beauty of human female, 127.

    Biologists accept evolution, 278.

    Bird colors, 131.

    Bird from reptile, 122.

    Bird nests, 145.

    Birds of a region definite, 61.

    Bird song, 135.

    Blowing viper, 107.

    Blue birds and frost, 61.

    Bradbury, Dean, 43.

    Buffon and evolution, 15.

    Bumble bees, 125.

    Butterfly colors, 129.

    Butterfly's mouth, 95.


    C

    Carboniferous age, 174.

    Carnivorous teeth, 124.

    Caterpillars on leaves, 110.

    Cave man, 188.

    Cells live in water, 166.

    Cenozoic age, 185.

    Cicada killer, 143.

    Circular nest of bird, 147.

    City life in man, 256.

    Clothing of birds, 101.

    Coal plants, 174.

    Cold-blooded animals, 99.

    Color, concealing, Thayer, 115.

    Concealing appearance, 105.

    Cope and Lamarckianism, 244.

    Cope on taste of toad, 118.

    Coral reef formation, 32.

    Country life in man, 256.

    Cretaceous period, 180.

    Cricket song, 134.

    Crinoids, 171.

    Crossing and variation, 53.

    Cuvier criticises Lamarck, 19.


    D

    Darwin, Charles,
      along La Plata, 28.
      at Buenos Ayres, 28.
      at Keeling Atoll, 31.
      at Galapagos, 30.
      father of evolution, 21.
      in Brazil, 27.
      in Patagonia, 29.
      in Peru, 30.
      on Beagle, 26.
      persuaded world of evolution, 21.
      studies Lyell's Geology, 26.
      studies Malthus, 35.

    Darwin, Erasmus, and evolution, 16.

    Darwin's ancestry, 22.
      birth, 23.
      burial in Abbey, 43.
      death, 43.
      education, 23.
      narrative of voyage, 33.
      patient mind, 45.
      purity of mind, 29.
      return to England, 33.
      short sketches, 39.
      study of barnacles, 34.
      work double, 233.

    Deer horns, 138.

    Descartes and evolution, 12.

    Descent of man, 189.

    Determinants in nucleus, 238.

    Development of chick, 204.

    Development of pond-snails, 46.

    Devonian age, 173.

    Devonian fish, 173.

    DeVries and mutation, 246.

    Duckmole, 208.


    E

    Early marriage, 272.

    Earth's age, 155.

    Ecstatic flight, 136.

    Egg-laying mammals, 208.

    Eimer and orthogenesis, 243.

    Elements of Geology, Lyell, 26.

    Emanuel Kant and evolution, 13.

    Embryo of chick, 203.

    Emerson and nature, 48.

    Empedocles and evolution, 8.

    English sparrow (see Sparrow, English).

    Environment in man, 258.

    Eugenic program, 269.

    Evening primrose and mutation, 246.

    Evolution since Darwin, 233.


    F

    Feeble-mindedness, 264.

    Feet of mammals, 122.

    First living things, 165.

    Fish eggs, 145.

    Fish may freeze, 104.

    Fitz-Roy, Capt., and Beagle, 25.

    Freedom of teaching, 291.

    Fright paralysis, 108.

    Frog's long tadpole stage, 112.

    Frost and bluebirds, 61.

    Fur of seal, 100.

    Future evolution of man, 249.


    G

    Galapagos Islands and evolution, 30.

    Geological periods, 158.

    Glyptodon and armadillo, 29.

    Goethe and evolution, 20.

    Graphite from plants, 168.

    Grasshopper's mouth, 93.

    Grasshopper song, 133.

    Groundhog and winter, 103.

    Growth of North America, 167.


    H

    Haeckel advocates evolution, 42.

    Health certificates, 263.

    Henslow and Darwin's education, 24.

    Henslow suggests Darwin for Beagle, 24.

    Heredity and natural selection, 45.

    Heredity in man, 258.

    Homes, few animals have, 98.

    Homes, warm-blooded animals, 101.

    Horn of rhinoceros, 123.

    Horns of deer, 138.

    Horse and early man, 232.
      earliest, 223.
      neck, 229.
      story of, 220.
      three-toed, 227.

    Horseshoe crab, 171.

    How mammals developed, 192.

    Huxley at Oxford meeting, 42.


    I

    Ichneumon fly, 142.

    Image of God, 288.

    Improving the environment, 259.

    Improving the stock, 261.

    Inheritance of acquired characters, 238.

    Insect's biting mouth, 93.

    Interpretation of Genesis, 284.

    Isolation, Jordan, 242.

    Isolation, Romanes, 242.

    Isolation, Wagner, 241.


    J

    Java skull, 187.

    Jehovah confounding the nations, 289.

    Jordan and isolation, 242.

    Judgment, Michael Angelo, 289.

    Jukes family, 265.

    June-bug, 107.


    K

    Kallikak family, 265.

    Kant and evolution, 13.

    Katydid's color, 111.

    Katydid's song, 133.

    Keeling Atoll and Darwin, 31.

    King Crab, 171.


    L

    Lamarck and evolution, 17.

    Lampshells, 172.

    La Place's theory, 151.

    Leibnitz, and evolution, 13.

    Life from other planets, 162.

    Life in the past, 149.

    Life, its nature, 247.

    Linnæan Society and evolution, 40.

    Linnæus and fixed species, 15.

    Locust's song, 135.

    Lucretius and evolution, 10.

    Lung-fish, 176.

    Lyell's Geology, 26.


    M

    Male birds brighter, 131.

    Male insects sing, 134.

    Malthus and population, 35.

    Mamma, significance of, 211.

    Mammals, egg-laying, 208.
      how developed, 192.

    Man and God's image, 288.
      early, and horse, 232.
      growing better, 255.

    Man's ancestry, 250.
      future evolution, 249.

    Mating and song, 133.

    Mating antics, 136.

    Meaning of Genesis, 284.

    Megatherium and sloth, 29.

    Mesozoic age, 178.

    Michael Angelo, Judgment, 289.

    Migration of birds, 103.

    Missing link, 187.

    Mizpah, 283.

    Modern teachers of biology, 291.

    Mongolian idiot, 265.

    Mosquito's bite, 97.

    Mosquito's mouth, 96.

    Mother-love, 217.

    Multiplication and evolution, 54.

    Mutation and DeVries, 246.


    N

    Nature of life, 247.

    Nature of milk, 214.

    Natural selection explained, 45.
      in brief, 36.

    Nebular hypothesis, 152.

    Neck of horse, 229.

    Neo-Darwinians, 237.

    Nests for warm eggs, 101.

    Number and position of breasts, 215.


    O

    Odor as protection, 117.

    Opossum playing dead, 107.

    Origin of birds, 181.
      feathers, 102.
      flight, 122.
      hair, 102.
      life, 159.
      lungs, 177.
      milk glands, 212.
      placenta, 210.
      variations, 50.

    "Origin of Species" published, 41.

    Orthogenesis and Eimer, 243.

    Oxford meeting of British Association, 41.


    P

    Palæozoic era, 170.

    Paley's Natural Theology, 87.

    Pangenesis, 236.

    Patagonia and its terraces, 29.

    Phenacodus, 185.

    Physical evolution of man, 254.

    Pithecanthropus, 188.

    Planetesimal theory, 155.

    Playing dead, 107.

    Playing 'possum, 107.

    Polygamy in animals, 137.

    Pond-snail, development of, 46.

    Potato worm, 142.

    Protective coloration, 109.

    Protoplasm, 164.

    Pterodactyl, 180.

    Puff adder, 107.

    Purpose and adaptation, 89.

    Purpose in nature, 88.


    Q

    Quiet and escape, 105.


    R

    Raining toads, 113.

    Religion and evolution, 74.

    Reptiles of Mesozoic, 179.

    Reproduction, asexual and sexual, 194.
      in fishes, 196.
      in frogs, 199.
      in reptiles, 202.

    Rhinoceros horn, 123.

    Romanes and isolation, 242.

    Rooster finer than hen, 132.


    S

    Saint Augustine and evolution, 11.

    Salamanders, 176.

    Sargent's picture, 289.

    Science and the book, 274.

    Science and theology, 280.

    Science, definition, 280.

    Seals and polygamy, 139.

    Sealskin and fur, 100.

    Sedgwick and Darwin, 24.

    Selection and evolution, 56.

    Sexual selection, 126, 128.

    Skunk's odor, 117.

    Sloth and megatherium, 29.

    Song and mating, 133.

    Sparrow, English, adapted to town, 66.
      and hawks, 69.
      and winter, 73.
      eat varied food, 71.
      eye-minded, 78.
      feed young on insects, 72.
      good qualities, 85.
      has reached limit, 85.
      in Philadelphia, 63.
      introduction, 62.
      lives near houses, 70.
      nests early, 81.
      nests often, 82.
      once migratory, 80.
      quarrels without animosity, 75.
      sociable, 74.
      spread of, 65.
      stays over winter, 79.
      successful, 83.
      transported in cars, 67.
      unafraid of man, 69.
      wintering, 73.

    Sparrow, House, 62.

    Sphex wasp, 143.

    Spider cocoons, 139.

    Spider, young, 140.

    Spontaneous generation, 159.

    Stone lilies, 171.

    Story of the horse, 220.

    Struggle against enemies, 104.
      for food, 91.
      for shelter, 92.
      for the individual, 90.
      for the species, 91, 125.

    Sunfish and young, 196.


    T

    Taste of toad, 118.

    Teeth of mammals, 98.

    Temperature of mammals, 99.

    Tertiary era, 185.

    Thayer, concealing color, 115.

    Theology and science, 280.

    Theology, definition, 280.

    Thomas Aquinas and evolution, 12.

    Three-toed horse, 227.

    Toad, bad taste, 118.
      color, 112.
      enemies, 113.
      short tadpole stage, 112.

    Tomato worm, 142.

    Turtles and young, 202.

    Tusks of elephant, 124.

    Tussock worm, 64.

    Two methods of reproduction, 194.

    Types of insect mouth, 93.


    U

    Understanding the Bible, 281.

    Underwing moth, 130.


    V

    Variation and natural selection, 49.
      by crossing, 53.

    Virchow and man's ancestry, 187.

    Vireo's color, 115.


    W

    Wagner and isolation, 241.

    Wallace and evolution, 39.

    Warm-blooded animals, 99.

    Weissman and evolution, 235.

    Wilberforce, Bishop, and evolution, 41.

    Wintering of ground hog, 103.

    Wintering of mammals, 103.

    Wintering of squirrels, 103.

    Woodchuck, 103.

    Woodpecker's nest, 146.


    Y

    Young growing finer, 272.



APPENDIX

BIBLIOGRAPHY


In connection with each chapter, wherever this is possible, there are
four classes of references. First is named a small and inexpensive but
satisfactory book on the subject. Second, a more comprehensive book,
readily accessible and not unduly expensive. Then a few of the most
satisfactory reference books on the subject independent of cost or
ready availability. Fourth, a list of references to articles in the
eleventh edition of the Encyclopedia Britannica.


CHAPTER I. _Evolution before Darwin._

1. -- -- -- --

2. Biology and Its Makers, Locy.

3. From the Greeks to Darwin, Osborn. Chapters 1, 2, 3, 19.

4. Encyclopedia Britannica, 11th edition, article, _Evolution_,
section, _History_.


CHAPTER II. _Darwin and Wallace._

1. The Coming of Evolution, Judd.

2. Charles Darwin, Poulton.

3. Life and Letters of Charles Darwin, by his son, Francis Darwin. 2
vols.

My Life, A. R. Wallace. 2 vols.

4. Encyclopedia Britannica, articles _Darwin_, _Wallace_.


CHAPTER III. _The Underlying Idea._

1. Evolution, Geddes and Thompson.

2. The Origin of Species, Charles Darwin.

3. The Evolution Theory, Weissmann. 2 vols.

4. Encyclopedia Britannica, articles _Variation_ and _Selection_.


CHAPTER IV. _Adaptation for the Individual._

1. Colin Clout's Calendar, Grant Allen.

2. Evolution and Animal Life, Jordan and Kellogg. Chapters 16, 19.

3. Darwinism, Wallace.

4. Encyclopedia Britannica, articles _Adaptation_, _Colours of
Animals_, _Hibernation_.


CHAPTER V. _Adaptation for the Species._

1. Colin Clout's Calendar, Grant Allen.

2. Evolution and Animal Life, Jordan and Kellogg.

3. Darwinism, Wallace.

4. Encyclopedia Britannica, articles, _Metamorphosis_, _Song of
Birds_.


CHAPTER VI. _Life in the Past._

1. The Story of Our Continent, Shaler.

2. Elements of Geology, Blackwelder and Barrows.

3. The Story of Evolution, McCabe.

4. Encyclopedia Britannica, article, _Geology_ (palæontological and
physiographical).


CHAPTER VII. _How the Mammals Developed._

1. -- -- -- --

2. Plant and Animal Children, Torelle.

3. -- -- -- --

4. Encyclopedia Britannica, article, _Mammalia_.


CHAPTER VIII. _The Story of the Horse._

1. The Evolution of the Horse in America, Osborn, in _The Century_,
November, 1904.

The Evolution of the Horse, Matthew.

2. The Horse, Flower.

3. Encyclopedia Britannica, article, _Horse_.


CHAPTER IX. _Evolution Since Darwin._

1. The Evolution of Living Organisms, Goodrich.

2. Biology and Its Makers, Locy. Chapters 14, 18.

3. Darwinism To-day, Kellogg.

4. Encyclopedia Britannica, articles, _Romanes_, _Weissmann_,
_Mendel_.


CHAPTER X. _The Future Evolution of Man._

1. The Problem of Race Regeneration, Ellis.

2. Inquiries into Human Faculty, Galton.

3. Heredity, Thompson.

4. Encyclopedia Britannica, articles, _Eugenics_, _Galton_.


CHAPTER XI. _Science and the Book._

1. -- -- -- --

2. The Origin and Permanent Value of the Old Testament, Skater.

3. The Life and Literature of the Ancient Hebrews, Abbott.

4. Encyclopedia Britannica, articles, _Genesis_, _Bible_ (Old
Testament Canon).


REVIEW QUESTIONS

_Foreword._ 1. What is the purpose of this book?

Chapter I. 1. What were some of the theories of the Greek
philosophers, and what shadowing of truth was there in their beliefs?
2. What was Lucretius's idea? 3. What were the explanations of Genesis
given by St. Augustine and by Thomas Aquinas? 4. What were theories of
Descartes, Leibnitz, and Kant? 5. How is the delay of the thought of
evolution accounted for? 6. What were the contributions of Linnæus,
Buffon, Erasmus, Darwin, Lamarck? 7. What check to progress was made
by Cuvier and Agassiz? 8. What phases of evolution were studied by
Goethe?

Chapter II. 1. Sketch the life of Charles Darwin. 2. What advantages
did he derive from the "Beagle" expedition? 3. What is the theory of
Natural Selection, and how did Darwin arrive at it? 4. Describe the
Wallace and Wilberforce incidents. 5. What has been the progressive
attitude toward the Darwinian idea?

Chapter III. 1. Explain Heredity as the conservative force of nature.
2. Explain Variation as the progressive tendency in nature. 3. In what
ratio is the Multiplication of animals? 4. How does the process of
Selection make for the survival of the fittest? 5. What three
possibilities are open to animals under a change of environment? 6.
What is the history of the English Sparrow in this country, and how is
his increase accounted for by his powers of adaptation?

Chapter IV. 1. Show how the struggle for existence as affecting food,
results in adaptations in the individual. Give illustrations. 2. Do
the same for the results of struggle for shelter. 3. What are some of
the adjustments resulting from the need of protection from foes?

Chapter V. 1. Discuss coloration. 2. How is sound used as an
attraction? 3. What are some of the other methods of attracting mates?
4. What are some of the specializations produced by polygamy? 5.
Describe some of the protections and provisions for the young.

Chapter VI. 1. What is La Place's Nebular Hypothesis? 2. What is the
Planetesimal Theory? 3. What bases have been used for calculation of
the age of the earth? 4. Reproduce the Table of Geological Times. 5.
What is the Theory of Spontaneous Generation? 6. What is the theory of
life development from organic dust in space? 7. Discuss protoplasm. 8.
What was the probable growth of the North American continent? 9. What
is the nature of the fossils in the earliest layers of stratified
rock? 10. Describe the life of each of the three periods of the
Palæozoic era. 11. Do the same for the Mesozoic era. 12. What was the
effect upon life of the development of seasons and of climates? 13.
What physical characteristics of the earth helped in the development
of new animal forms in the Cenozoic era? 14. What has been the ascent
of man?

Chapter VII. 1. Illustrate the asexual method of reproduction. 2.
Trace the two-parent method of reproduction upward from the simplest
forms. 3. What has been the development of the milk glands? 4. How
does the prolonged care of the young by the mother indicate the higher
development of the animal?

Chapter VIII. 1. Describe the earliest known ancestor of the horse? 2.
What changes took place in the second stage of development? 3. What is
the form by the middle of the Tertiary period? 4. What was the size of
the late Tertiary horse, and how was the grinding power of the teeth
increased? 5. How was the early Quaternary horse adapted for speed and
for eating? 6. How is the extermination of the horse in North and
South America accounted for, and how was he introduced again?

Chapter IX. 1. How extensive has the belief in evolution become since
Darwin's day? 2. How does the theory of Natural Selection fail in
accounting for Variation; how did Darwin try to amend his original
theory; and what is Weissmann's belief. 3. What second objection has
been brought against the theory of Natural Selection, and what have
been the contributions of Wagner, Jordan, and Romanes to the
discussion? 4. What is the third objection to Darwinism, and what is
the bearing upon it of the theory of Orthogenesis? 5. What is the
American and French tendency toward the belief that use is the cause
of the persisting of organs? 6. How did DeVries discover the
principle of mutation, and how does it apply to the discussion of
evolution?

Chapter X. 1. What was the cause of the passing of the civilization of
Athens, of Judea, of Sparta? 2. What promise of uniform development is
evident to-day, and what are some of the hindrances? 3. What has been
the changing emphasis in the evolution of man? 4. How is man the
arbiter of his own destiny? 5. What is the task of the eugenist; how
is he trying to accomplish it, and what are some of the possibilities
suggested. 6. What is the promise for the future?

Chapter XI. 1. What is the duty of the fair-minded person toward the
essential truths of religion and of science? 2. What two difficulties
lie in the path of reconciliation, and why should each century restate
its truths? 3. What three steps are desirable in studying the Bible?
Illustrate. 4. What is the essential truth of the early chapters of
Genesis, and what its glory? 5. Interpret the meaning of "creation of
man in God's image." 6. What is our duty to ourselves and our
children?





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