Chapter II: Part 2

"According to the theory of development (evolution) in its simplest form," says Henry Hartshorne,[18] "the universe as it now exists is a result of 'an immense series of changes,' related to and dependent upon each other as successive steps, or rather growths, constituting a progress; analogous to the unfolding or evolving of the parts of a growing organism." Herbert Spencer defined evolution as consisting in a progress from the homogeneous to the heterogeneous, from general to special, from the simple to the complex; and this process is considered to be traceable in the formation of worlds in space, in the multiplication of the types and species of plants and animals on the globe, in the origination and diversity of languages, literature, arts and sciences, and in all changes of human institutions and society.

Let us now apply this theory of evolution to the physical world. No determined opposition by the mass of people is likely to be manifested to the doctrine of evolution as applied to the physical world, or even to the vegetable or animal world up to man; but the minute man is included--then is a voice raised up against it, and it was for this reason that Darwin in his first work on the "Theory of Descent" did not mention man as being included in the evolutionary series. He knew too well the foolish human weakness that existed.

In a recent work by Prof. Challes, he states that he regards the material universe as "a vast and wonderful mechanism of which the least wonderful thing is its being so constructed that we can understand it."

The following is a brief description of the various theories of the world's formation:

_First Theory._--By the first theory the world is supposed to have existed from eternity under its actual form. Aristotle embraced this doctrine, and conceived the universe to be the eternal effect of an eternal cause; maintaining that not only the heavens and the earth, but all animate and inanimate beings, are without beginning. To use Huxley's illustration: If you can imagine a spectator on the earth, however far back in time, he would have seen a world "essentially similar, though not perhaps in all its details, to that which now exists. The animals which existed would be the ancestors of those which now exist, and like them; the plants in like manner would be such as we have now, and like them; and the supposition is that, at however distant a period of time you place your observer, he would still find mountains, lands, and waters, with animal and vegetable products flourishing upon them and sporting in them just as he finds now." This theory being perfectly inconsistent with facts, had to be abandoned.

_Second Theory._--The second theory considers the universe eternal, but not its form. This was the system of Epicurus and most of the ancient philosophers and poets, who imagined the world either to be produced by fortuitous concourse of atoms existing from all eternity, or to have sprung out of the chaotic form which preceded its present state.

_Third Theory._--By this theory the matter and form of the earth is ascribed to the direct agency of a spiritual cause. It is needless to say that this last theory has for its basis the popular account, generally credited to Moses in the first chapter of Genesis. I say popular, for it certainly is not a scientific account, nor was it the intention of the writer to make it so. The supposed object was to show the relation between the Creator and his works. If it had been an ultimate scientific account, the ablest minds of to-day would be unable to comprehend it, as science is progressive and constantly changing; in fifty thousand years to come, it would still appear utterly absurd. It cannot be said for this fact that the account is any the less true because it is not presented in scientific phraseology; for instance, when we remark in popular language "the sun rises," who shall say that though the expression is not astronomically true, we do not, for all practical purposes, utter as important a truth, as when we say, "The earth by its revolution brings us to that point where the sun becomes visible?" The language, also, in which the writer wrote was very imperfect; it had no equivalent to our word "air" or "atmosphere," properly speaking, for they knew not the words. "Their nearest approaches," according to J. Pye Smith, "were with words that denoted watery vapor condensed, and thus rendered visible, whether floating around them or seen in the breathing of animals; and words for smoke from substances burning; and for air in motion, wind, a zephyr whisper or a storm." It must also be remembered, "that the Hebrews had no term for the abstract ideas which we express by 'fluid' or 'matter.' If the writer had designed to express the idea, 'In the beginning God created _matter_,' he could not have found words to serve his purpose" (Phin).

It is unnecessary to state how the Bible, which contains the so-called Mosaic account, is regarded by the different church denominations, as undoubtedly that is familiar to every one. But with respect to the view entertained by the scientist and critical school of Biblical scholars, represented chiefly by modern Germans, I may state briefly: "They regard the Bible as the human record of a divine revelation; not absolutely infallible, since there is no book written in any human language but must partake in a measure of the imperfections of that language. Many of this school, while admitting the Bible to contain the record of a true supernatural revelation, do not consider it to be without positive error of historical fact, not without false coloring from popular legend and tradition, but nevertheless a record as good as human hands could make a truly divine revelation."[19]

There is, though, a class of thinkers that altogether reject the Bible; that is to say, refuse to believe it to be a divine revelation. Hume, whom Huxley calls "the most acute thinker of the eighteenth century," thus ends one of his essays: "If we take in hand any volume of divinity or school metaphysics, for instance, let us ask, _Does it contain any abstract reasoning concerning quantity or number?_ No. _Does it contain any experimental reasoning concerning matter of fact and existence?_ No. Commit it, then, to the flames, for it can contain nothing but sophistry and illusion." To this Huxley says: "Permit me to enforce this wise advice, Why trouble ourselves about matters of which, however important they may be, we do know nothing, and can know nothing? We live in a world which is full of misery and ignorance, and the plain duty of each and all of us is to try to make the little corner he can influence somewhat less miserable and somewhat less ignorant than it was before he entered it. To do this effectually, it is necessary to be fully possessed of only two beliefs: the first, that the order of nature is ascertainable by our faculties to an extent which is practically unlimited; the second, that our volitions count for something as a condition of the course of events. Each of these beliefs can be verified experimentally, as often as we like to try. Each, therefore, stands upon the strongest foundation upon which any belief can rest, and forms one of our highest truths."

The first words in the Mosaic account are:[20] "In the beginning God created the heaven and the earth."[21] It is seen, then, that the so-called revelation points to a beginning. The beginning referred to is an absolute beginning, for we find: "In the beginning was the Word, and the Word was with God, and the Word was God."[22] * * * "All things were made by Him; and without Him was not anything made that was made."[23] Science points also to a beginning.

Geology points to a time when man did not inhabit the earth; when for him there was a beginning. So, too, for lower organisms; so, too, for the rocky minerals; so, too, for the round world itself. But the beginning that science points to is not an absolute beginning. Science has to start from some point, and that point must have a scientific foundation--the foundation of science is matter, which is inseparable from form and force. Natural science teaches that matter is eternal and imperishable; for experience has never shown us that even the smallest particle of matter has come into existence or passed away. "A naturalist," says Haeckel, "can no more imagine the coming into existence of matter than he can imagine its disappearance, and he therefore looks upon the existing quantity of matter in the universe as a given fact." "The creation of matter, if, indeed," says Haeckel,[24] "it ever took place, is completely beyond human comprehension, and can therefore never become a subject of scientific inquiry. We can as little imagine a _first beginning_ of the eternal phenomena of the motion of the universe as of its final end."[25] It is evident, then, that the absolute beginning of the universe and its absolute end are not questions of science, and can be known only as revealed by faith. Paul says: "By faith we understand that the world was framed by the word of God, so that things which are seen were not made of things which appeared."[26]

The natives of Borneo pretend that these monkeys, or, as sometimes called, Kahan, are men who have retired to the woods to avoid paying taxes; and they entertain the greatest respect for a being who has found such ready means of evading the responsibilities of society.--_Figuier._]

FIG. I.--Photographically reduced from diagrams of the natural size (except that of the Gibbon, which was twice as large as nature), drawn by _Waterhouse Hawkins_, from specimens in the museum of the Royal College of Surgeons. (_Huxley's_ "Man's Place in Nature.")]

If, therefore, science makes the "history of creation" its highest and most difficult and most comprehensible problem, it must deal with "_the coming into being of the form_ of natural bodies." Let us look for a minute at Kant's Cosmogony, or, as Haeckel says,[27] Kant's Cosmological Gas Theory: "This wonderful theory," says Haeckel, "harmonizes with all the general series of phenomena at present known to us, and stands in no irreconcilable contradiction to any one of them. Moreover, it is purely mechanical and monistic, makes use exclusively of the inherent forces of eternal matter, and entirely excludes every supernatural process, every prearranged and conscious action of a personal creator." Compare this last statement with the following: "I will, however," says Haeckel,[28] "not deny that Kant's grand cosmogony has some weak points." * * * "A great unsolved difficulty lies in the fact that the cosmological gas theory furnishes no starting-point at all in explanation of the first impulse which caused the rotary motion in the gas-filled universe."

Whewell[29] has pointed out, that the nebular hypothesis is null without a creative act to produce the inequality of distribution of cosmic matter in space.

It is seen, then, that according to Kant's theory we are to suppose that millions of years ago there appeared a nebulous mass possessing a rotary motion, and unequally distributed through space. This is what science calls a beginning, and may assert that every physical event of a hundred million of ages existed potentially in that nebulous mass. But this is really no explanation of the ultimate and real cause of anything. Reason demands the cause of this beginning, the source that gave to the nebulous mass its rotary motion; the power that distributed the matter in space; the antecedents of the cosmical vapor. In absence of antecedents, what was the cause of this fire-mist--of these forces active in it? Reason will never remain satisfied until these questions are answered. But physical science can trace the thread no further back, and must be dumb to all ulterior inquiries. It is true, then, as physicists assert, "that their science does not mount actually to God."

To God then, in strict accordance with our reason, is to be attributed not only the origination of matter, but all its future developments. When I speak of matter, it must be understood that I mean force; for "if matter were not force, and immediately known as force, it could not be known at all, could not be rationally inferred. The operation of force could furnish no evidence of the existence of forceless matter. If force is not matter, then force can exist and operate without matter; its existence and operation are no evidence of the existence of matter. And as matter is forceless, it can itself give no evidence of its own existence, for that would be an exercise of force. If force cannot exist and operate without matter, then force depends for its existence and operation on the forceless, which destroys itself; or force depends for its existence on matter as some property or force, and so matter and force are identified, and force depends on itself only, as it must."[30] The idea, then, that force is an attribute of matter and inherent in it, is absurd, for there is not a shadow of evidence that force is or can be an attribute of matter. We have no knowledge of the origin of any force save of that which emanates from human volition. All our knowledge of force presents it as an effort of intelligent will. "We are driven," says Winchell, "by the necessary laws of thought, to pronounce those energies styled gravitation, heat, chemical affinity and their correlates, nothing less than intelligent will. But as it is not human will which energizes in whirlwind and the comet, it must be divine will." "In all cases, the creative power of God is an act of power, and the power does not perish with its inception, but continues to operate until the act is reversed and undone; so that everything that God has created constitutes a positive and intrinsic force, though borrowed from Him. Every incident runs back to God as its originator and real cause. The true philosophical doctrine makes God distinct from all his works, and yet acting in them. This doctrine has been held by the greatest thinkers the world has ever produced, such as Descartes, Lerbrisky, Berkeley, Herschel, Faraday, and a multitude of others." "It seems to be required," says Dr. McCosh, "by that deep law of causation which not only prompts us to seek for a law in everything but an adequate cause, to be found only in an intelligent mind." "Our greatest American thinker, Jonathan Edwards," says Dr. McCosh, (whom I can claim as my predecessor,) "maintains that, as an image in a mirror is kept up by a constant succession of rays of light, so nature is sustained by a constant forth-putting of the divine power. In this view Nature is a perpetual creation. God is to be seen not only in creation at first, but in the continuance of all things." "They continue to this day according to Thine ordinances."

Returning now to the history of the creation given by Moses, Haeckel says, "Although Moses looks upon the results of the great laws of organic development as the direct actions of a constructing Creator, yet in his theory there lies hidden the ruling idea of a progressive development and a differentiation of the originally simple matter. We can therefore bestow our just and sincere admiration on the Jewish lawgiver's grand insight into nature, without discovering in it a so-called 'divine revelation.' That it cannot be such is clear from the fact that two great fundamental errors are asserted in it, namely, first the _geocentric_ error, that the earth is the fixed central point of the whole universe, round which the sun, moon and stars move; and secondly, the _anthropocentric_ error that man is the premeditated aim of the creation of the world, for whose service alone all the rest of nature is said to have been created. The former of these errors was demolished by Copernicus' System of the Universe in the beginning of the sixteenth century, the latter by Lamarck's Doctrine of Descent in the beginning of the nineteenth century."

Prof. Huxley, in his lecture on "Evidences of Evolution," spoke of the Mosaic account as Milton's hypothesis. First, "because," says Huxley, "we are now assured upon the authority of the highest critics, and even of dignitaries of the church, that there is no evidence whatever that Moses ever wrote this chapter, or knew anything about it;" and second, as this hypothesis is presented in Milton's work on "Paradise Lost," it is appropriate to call it the Miltonic Hypothesis. "In the Miltonic account," says Huxley, "the order in which animals should have made their appearance in the stratified rocks would be this: Fishes, including the great whale, and birds; after that all the varieties of terrestrial animals. Nothing could be further from the facts as we find them. As a matter of fact we know of not the slightest evidence of the existence of birds before the jurassic and perhaps the triassic formations. If there were any parallel between the Miltonic account and the circumstantial evidence, we ought to have abundant evidence in the devonian, the silurian, and carboniferous rocks. I need not tell you that this is not the case, and that not a trace of birds makes its appearance until the far later period which I have mentioned. And again, if it be true that all varieties of fishes, and the great whales and the like, made their appearance on the fifth day, then we ought to find the remains of these things in the older rocks--in those which preceded the carboniferous epoch. Fishes, it is true, we find, and numerous ones; but the great whales are absent, and the fishes are not such as now live. Not one solitary species of fish now in existence is to be found there, and hence you are introduced again to the difficulty, to the dilemma, that either the creatures that were created then, which came into existence the sixth day, were not those which are found at present, or are not the direct and immediate predecessors of those which now exist; but in that case you must either have had a fresh species of which nothing has been said, or else the whole story must be given up as absolutely devoid of any circumstantial evidence."

It is for these and many other reasons that I feel bound to omit the Mosaic account, no matter how near some portions of it coincide with the facts the earth has opened out to the scientist.

KANT'S COSMOGONY.

It is maintained by Kant's Cosmogony that every substance, be it solid or liquid, constituting the entire universe, was, inconceivable ages ago, in their homogeneous gaseous or nebulous condition. Owing to an impulse being given to the nebulous mass, it acquired a rotary movement, which divided the nebulous mass up into a number of masses which, owing to the rotation, acquired greater density than the remaining gaseous mass, and then acted on the latter as central points of attraction. Our solar system was thus a gigantic gaseous or nebulous ball, all the particles of which revolved around a common central point--the solar nucleus. This nebulous ball assumed by its continual rotation a more or less flattened spheroidal form. By the continual revolution of this mass, under the influence of the centripetal and centrifugal forces, a circular nebular ring separated (like the present ring around Saturn) from the rotating ball. In time the nebulous ring condensed to a planet, which began to revolve around its own axis. When the centrifugal force became more powerful than the centripetal force in the planet, rings were formed, which, in turn, formed planets which revolved around their axes, as also around their planets, as the latter moved around the sun, and thus arose the moons, only one of which moves around our earth, while four move around Jupiter and six around Uranus. This order of things was repeated over and over again until thereby arose the different solar systems--the planets rotating around their central suns, and the satellites or moons moving around their planets. By a continuous increasing of refrigeration and condensation, a fiery fluid or molten state occurred in these rotating bodies. They then emitted an enormous amount of heat by rapid condensation, and the rotating bodies--suns, planets, and moons--soon became glowing balls of fire, emitting light and heat. The 1/1000 part of a pound of magnesium wire, burning in the open air, will give a light which will last during one second, and can be seen at a distance of thirty miles; imagine, then, what the light would be from these huge balls of fire floating through space. The earth forms a small part--nay, even the sun whose mass is equal to 354,936 earths like ours, is but an infinitesimal portion of the whole. By the continual emitting of heat, however, these fiery balls had a crust form on the outside, which enclosed a fiery fluid nucleus. The crust for a time must have been a smooth sheet, but afterward very uneven, having protuberances and cavities form over its surface, owing to the molten mass within becoming condensed and contracted; the crust not following this change sufficiently close, must have fallen in, and thus produced the cavities.

All the time, by the condensation, the diameter of the earth was being diminished. The irregular cooling of the crust caused irregular contractions on the surface, and as the diameter of the molten mass within was continually diminishing, many elevations and depressions were caused, which were the foundations of mountains and valleys.

After the temperature of the earth had been reduced by the thickening of the crust--when it became sufficiently cool--the water which existed in steam was condensed and precipitated, falling in torrents, washing down the elevations, filling the depressions with the mud carried along, and depositing it in layers. It was not until the earth became covered with water that life was possible in any form, as both animals and plants consist to a very great extent of water. At this stage in the history of the earth, then, the little mass of protoplasm, which we have spoken so much about, came into existence in all probability, as has been stated, by spontaneous generation.

LAWS OF EVOLUTION.

Let us now examine some of the laws of evolution, as also some of the connecting links which blend one stage of man's development with another, which at first thought would seem unexplainable.

Haeckel[31] summarizes the inductive evidences of Darwinism as follows: 1. Paleontological series (phylogeny); 2. Embryological development of the individual (ontogeny); 3. The correspondence in the terms of these two series; 4. Comparative anatomy (typical forms and structures); 5. Correspondence between comparative anatomy and ontogeny; 6. Rudimentary organs (dipeliology); 7. The natural system of organisms (classification); 8. Geographical distribution (chorology); 9. Adaptation to the environment (oecology); 10. The unity of biological phenomena.

It will of course be impossible to consider even hastily all of the inductive evidence belonging to the several groups mentioned above, for the scope of this work would not permit of it. Only such facts as present themselves most forcibly to the mind will be considered.

Darwinism, as has already been stated, is not the doctrine of evolution; it is, however, a successful attempt to explain the law or manner of evolution. The _law of natural selection_, pointed out by Darwin, is called by Herbert Spencer, _The struggle for existence_. Darwin discovered that natural selection produces fitness between organisms and their circumstances, which explains the law of _the survival of the fittest_.

It is a well-known fact that man can, by pursuing a certain method of breeding or cultivation, improve and in various ways modify the character of the different domestic animals and plants. By always selecting the best specimen from which to propagate the race, those features which it is desired to perpetuate become more and more developed; so that what are admitted to be real varieties sometimes acquire, in the course of successive generations, a character as strikingly distinct, to all appearances, from those of the varieties, as one species is from another species of the same genus. It is evident that both natural and artificial selection depends on adaptation and inheritance. The difference between the two forms of selection is that, in the first case, the will of man makes the selection according to a plan, whereas in natural selection the struggle for life and the survival of the fittest acts without a plan other than that the most adaptable organism shall survive which is most fit to contend with the circumstances under which it is placed. Natural selection acts, therefore, much more slowly than artificial selection, although it brings about the same end. Adaptation in the struggle for life is an absolute necessity.

In every act of breeding, a certain amount of protoplasm is transferred from the parents to the child, and along with it there is transferred the individual peculiar molecular motion. Adaptation or transmutation depends upon the material influence which organism experiences from its surroundings, or its conditions of existence; while the transmission from inheritance is due to the partial identity of producing and produced organisms.

Organized beings, as a rule, are gifted with enormous powers of increase. Wild plants yield their crop of seed annually, and most wild animals bring forth their young yearly or oftener. Should this process go on unchecked, in a short time the earth would be completely overrun with living beings. It has been calculated that if a plant produces fifty seeds (which is far below the reproductive capacity of many plants) the first year, each of these seeds growing up into a plant which produces fifty seeds, or altogether two thousand five hundred seeds the next year, and so on, it would under favorable conditions of growth give rise in nine years to more plants by five hundred trillions than there are square feet of dry land upon the surface of the earth.

Slow-breeding man has been known to double his number in twenty-five years, and according to Euler, this might occur in little over twelve years. But assuming the former rate of increase, and taking the population of the United States at only thirty millions, in six hundred and eighty-five years their living progeny would have each but a square foot to stand upon, were they spread over the entire globe, land and water included. But millions of species are doing the same thing, so that the inevitable result of this strife cannot be a matter of chance. Evidently those individuals or varieties having some advantage over their competitors will stand the best chance to live, while those destitute of these advantages will be liable to destruction. Nature may be said (metaphorically) to choose (like the will of man in artificial selection) which shall be preserved and which destroyed.

That portion of the theory of development which maintains the common descent of all species of animals and plants from the simplest common origin, I have already stated with full justice should be called Lamarckism. Progress is recognized by all scientists to be a law of nature. Some of the more important facts which sustain the theory of development, I propose now to present as briefly as possible.

RUDIMENTARY ORGANS.

One of the strongest arguments in favor of the hypothesis of a genetic connection among all animals (including man), at least among all those belonging to the same great types, is the presence of rudimentary parts. By rudiments in anatomy are meant organs or structures imperfectly developed, so as to be almost or entirely without functional use. "Each of them represents in germ, as it were, in one animal (or plant), that which is perfect and useful in another type."

For a few examples: The little fold of caruncle at the inner margin of the eye in man, represents the nictitating membrane of birds. Eyes which do not see form a striking example. These are found in very many animals which live in the dark, as in caves or underground. Their eyes are often perfectly developed but are covered by a membrane, so that no ray of light can enter and they can never see. Such eyes, without the function of sight, are found in several species of moles and mice which live underground, in serpents and lizards, in amphibious animals (proteus, cæcilia) and in fishes; also in numerous invertebrate animals which pass their lives in the dark, as do many beetles, crabs, snails, worms, etc.

Other rudimentary organs are the wings of animals which cannot fly. For example, the wings of the running birds, like the ostrich, emeu, cassowary, etc., the legs of which become exceedingly developed. The muscles which move the ears of animals are still present in man, but of course are of no use; by continual practice persons have been able to move their ears by these muscles. The rudiment of the tail of animals which man possesses in his 3-5 tail vertebræ, is another rudimentary part--in the human embryo it stands out prominently during the first two months of its development; it afterwards becomes hidden. "The rudimentary little tail of man is irrefutable proof that he is descended from tailed ancestors." In woman the tail is generally, by one vertebra, longer than in man. There still exists rudimentary muscles in the human tail which formerly moved it.

Another case of human rudimentary organs, only belonging to the male, and which obtains in like manner in all mammals, is furnished by the mammary glands on the breast, which, as a rule, are active only in the female sex. However, cases of different mammals are known, especially of men, sheep and goats, in which the mammary glands were fully developed in the male sex, and yield milk as food for their offspring. The vermiform appendix of the large intestine in man, is another illustration of a part which has no use, but in one marsupial is three times the length of its body. The rudimentary covering of hair over certain portions of the body, is not without interest. Over the body we find but a scanty covering, which is thick only on the head, in the armpits, and on some other parts of the body. The short hairs on the greater part of the body are entirely useless, and are the last scanty remains of the hairy covering of our ape ancestors. Both on the upper and lower arm the hairs are directed toward the elbow, where they meet at an obtuse angle--this striking arrangement is only found in man and the anthropoid apes, the gorilla, chimpanzee, orang, and several species of gibbons. The fine short hairs on the body become developed into "thickset, long, and rather coarse dark hairs," when abnormally nourished near old-standing inflamed surfaces.[32] The fine wool-like hair or so-called lanugo with which the human foetus, during the fifth and sixth months, is thickly covered, offers another proof that man is descended from an animal which was born hairy, and remained so during life. This covering is first developed during the fifth month, on the eyebrows and face, and especially around the mouth, where it is much longer than that on the head. Three or four cases have been recorded of persons born with their whole bodies and faces thickly covered with fine long hairs. Prof. Alex. Brandt compared the hair from the face of a man thus characterized, aged thirty-five, with the lanugo of a foetus, and finds it quite similar in texture. Eschricht[33] has devoted great attention to this rudimentary covering, and has thrown much light on the subject. He showed that the female as well as the male foetus possessed this hairy covering, showing that both are descended from progenitors, both sexes of whom were hairy. Eschricht also showed, as stated above, that the hair on the face of the fifth month foetus is longer on the face than on the head, which indicates that our semi-human progenitors were not furnished with long tresses, which must therefore have been a late acquisition. The question naturally arises, is there any explanation for the loss of hair covering?

Darwin is of the opinion that the absence of hair on the body is, to a certain extent, a secondary sexual character; for, in all parts of the world, women are less hairy than men. He says: "Therefore we may reasonably suspect that this character has been gained through sexual selection." As the body in woman is less hairy than in man, and as this character is common to all races, we may conclude that it was our female semi-human ancestors who were first divested of hair.

Professor Grant Allen[34] has given much study to the subject of the loss of hair in the human being; and his investigations are worthy of careful consideration. He shows conclusively that those parts of an animal which are in constant contact with other objects are specially liable to lose their hair. This is noticeable on the under surface of the body of all animals which habitually lie on the stomach. The soles of the feet of all mammals where they touch the ground are quite hairless; the palms of the hands in the quadrumana present the same appearance. The knees of those species which frequently kneel, such as camels and other ruminants, are apt to become bare and hard-skinned. The friction of the water has been the means of removing the hair from many aquatic mammals--the whales, porpoises, dugongs, and manatees are examples.

As the back of man forms the specially hairless region of his body, we must conclude that it is in all probability the first part which became entirely denuded of hair. The gorilla, according to Professor Gervais, is the only mammal which agrees with man in having the hair thinner on the back, where it is partly rubbed off, than on the lower surface. Du Chaillu states that he has "himself come upon fresh traces of a gorilla's bed on several occasions, and could see that the male had seated himself with his back against a tree-trunk." He also says: "In both male and female the hair is found worn off the back; but this is only found in very old females. This is occasioned, I suppose, by their resting at night against trees, at whose base they sleep." The gorilla has only very partially acquired the erect position, and probably sits but little in the attitude common to man. In man the case is different; in proportion as his progenitors grew more and more erect, he must have lain less and less upon his stomach, and more and more upon his back or sides, and this is seen in the savage man during his lazy hours--who stretches himself on the ground in the sun, with his back propped, where possible, by a slight mound or the wall of his hut. The continual friction of the surface of the back would arrest the growth of hair; for hair grows where there is normally less friction, and _vice versâ_.

As man became more and more hairless, especially among savage and naked races, we should conclude that such a modification would be considered a beauty, and women would select such men in preference to more hairy individuals. The New Zealand proverb is: "There is no woman for a hairy man." Sexual selection, then, would play a very important part; and the difficulty of understanding how man became divested of hair is readily explained.

Haeckel says: "Even if we knew absolutely nothing of the other phenomena of development, we should be obliged to believe in the truth of the theory of descent, solely on the ground of the existence of rudimentary organs."

REPRODUCTION BY MEANS OF EGGS.

It might be thought there existed a missing link between animals which lay eggs and those which do not; this, however, is done away with in many instances--one, for example, is found in our commonest indigenous snake. The ringed snake lays eggs which require three weeks time to develop; but when it is kept in captivity, and no sand is strewn in the cage, it does not lay eggs, but retains them until the young ones are developed. This only shows how powerfully influences affect the habit of animals.

DOUBLE-SEXED INDIVIDUALS.

Another difficulty might be supposed to arise between animals which produce themselves other than by sexual reproduction. This has already been slightly touched upon; and it has been shown that numerous plants and animals propagate themselves through their double-sexed organs. It occurs in a great majority of plants, but only in a minority of animals; for example, the garden-snail, leeches, earth-worms, and many other worms. Every garden-snail produces in one part of its sexual gland eggs, and in another part sperm.

Parthenogenesis offers an interesting form of transition from sexual reproduction to the non-sexual formation of germ-cells (which most resembles it). It has been demonstrated to occur in many cases among insects, especially by Seebold's excellent investigations. Among the common bees, a male individual (a drone) arises out of the eggs of the queen, if the eggs have not been fructified; a female (a queen or working bee), if the egg has been fructified.

Gonochorismus or sexual separation, which characterizes the more complicated of the two kinds of sexual reproduction, has evidently been developed from the condition of hermaphroditism at a late period of the organic history of the world. In this case the female individual in both animal and plant produces eggs or egg-cells. In animals, the male individual secretes the fructifying sperm (sperma); in plants, the corpuscles, which correspond to the sperm.

INHERITANCE.

The remarkable facts of inheritance, extending to the reproduction of unimportant peculiarities of parts or organs (rudimentary parts) mentioned above, and the occasional outbreak of ancestral characters that have been dormant through several generations (some of which I will mention further on), might be thought perfectly unexplainable; but they are readily accounted for by the supposition that each part of an organism contributes its constituent and effective molecules to the germ and sperm particles. Mr. Sorby made numerous investigations with relation to the number of molecules in the germinal matter of eggs, and the spermatic matter supplied by the male. Omitting the alkali, Mr. Sorby takes the formula, C{72}H{112}N{18}SO{22}, as representing the composition of albumen. In a 1/2000 of an inch cube, he reckons--

Albumen 18,000,000,000,000 molecules.
Water 992,000,000,000,000 "
--------------------------------
1,010,000,000,000,000 molecules.

Or, in a sphere of the same diameter, 530,000,000,000,000 of the two components. Taking a single mammalian spermatozoon, having a mean diameter of 1/6000 of an inch; "it might contain two and a half million of such gemmules. If these were lost, destroyed, or fully developed at the rate of one in each second, this number would be exhausted in about one month; but since a number of spermatozoa appears to be necessary to produce perfect fertilization, it is quite easy to understand that the number of gemmules introduced into the ovum may be so great that the influence of the male parent may be very marked, even after having been, as regards particular character, apparently dormant for many years." The germinal vesicle of a mammalian ovum being about 1/1000 of an inch, mean diameter, might contain five hundred million of gemmules, which, if used up at the rate of one per second, would last more than seventeen years. If the whole ovum, about 1/150 in diameter, were all gemmules, the number would be sufficient to last, at this rate, one per second for 5,600 years! This, however, is not probable; but Mr. Sorby's remarks has completely removed all doubt as to its physical possibility from the Darwinian theory; "and they prompt us," says Slack, "to a wonderful conception of the powers residing in minute quantities of matter."

The laws of inheritance are divisible into two series, conservative and progressive transmission; the laws of adaptation to direct (active) or indirect (potential) adaptation.

External causes often influence the reproductive system, especially in organism propagating in a sexual way. This can be strikingly shown in artificially produced monstrosities. Monstrosities can be produced by subjecting the parental organism to certain extraordinary conditions of life; and curiously enough, such an extraordinary condition of life does not produce a change of the organism itself, but a change in its descendants. The new formation exists in the parental organism only as a possibility (potential); in the descendants it becomes a reality (actual). Most commonly, monstrosities with very abnormal forms are sterile, but there are instances where they reproduce their kind and become a species.[35] Geoffroy St. Hilaire, who perhaps made the deepest investigations ever conducted into the nature and causes of their production, first conceived the idea of artificially producing them, and to this end he began modifications of the physical conditions of the evolution of the chicken during natural and artificial incubation. He determined the fact that monsters could be produced in this way, but scarcely carried his investigation further. This work has been taken up by M. Dareste, and he has lately published a volume in Paris which recounts the results of a quarter of a century's experimenting. Eggs, he states, were submitted to incubation in a vertical instead of a horizontal position; they were covered with varnish in certain places so as to stop or modify evaporation and respiration. The evolution of the chick was rendered slower by a temperature below that of the normal heat of incubation. Finally, eggs were warmed only at one point, so that the young animal, during development, was submitted at different parts to variable temperatures.

These perturbations resulted in the most curious and unlooked for deformities in the embryo, some being not alone peculiar to the bird, but being similar to those which have been recognized in many other animals, and even in the human species. The data obtained have been deemed so important that M. Dareste has recently received the Lacaze prize for physiology from the French Academy of Sciences.

It would be impossible to review even a fraction of the many forms of monstrosities which M. Dareste has discovered. Those that we give will, however, suffice to convey an idea of the wonderful variations produced. Fig. 1 is a chick embryo with the encephalon entirely outside the head, the heart, liver, and gizzard outside the umbilical opening, right wing lifted up beside the head, and the development of the left one stopped. In Fig. 2 the encephalon is herniated and marked with blood spots, the eye is rudimentary and replaced by a spot of pigment, the upper beak is shorter than the lower one, while the heart, liver, etc., are all outside. In Figs. 3 and 4 the head is compressed, eyes well developed, but in the back instead of in the sides of the head; the body is bent, abdominal intestines not closed, heart largely developed and herniated. The literal references to the foregoing are: _am_, amnion; _al_, allantois; _v_, vitellus; _h_, encephalon; _i_, eye; _c_, heart; _f_, liver; _g_, gizzard; _ms_, upper, and _mi_, lower member.

The commonest case of monstrosity observed by M. Dareste has been that of the head protruding from the navel, and the heart or hearts above the head. This is a most extraordinary and new monster, and, if it persist, a chicken with its heart on its back, like a hump, may be expected. A curious fact discovered is the duplicity of the heart at the beginning of incubation, two hearts, beating separately, being clearly seen. Another anomaly consists in heads with a frontal swelling, which is filled by the cerebral hemispheres.

M. Dareste's artificial monsters are all produced from the single germ or cicatricule (as the white circular spot seen in the yellow of the egg, and from which the embryo springs, is termed). He has not yet been able to determine artificially the production of monsters, the origin of which takes place in a peculiar state of the cicatricule before incubation. But having submitted to incubation some 10,000 eggs, he has obtained several remarkable examples of double monstrosities in process of formation, some representations of which are given herewith. Fig. 5 shows three embryos, all derived from a single cicatricule. Fig. 6 represents three embryos from two cicatricules. On one side of the line of junction are two imperfectly developed embryos, one having no heart. The single embryo on the other side is generally normal, but has a heart on the right side. In Fig. 7 are twins, one well formed, the heart circulating colorless blood, the other having no heart and a rudimentary head. Fig. 8 exhibits a double monster with lateral union. The heads are separate, and there are three upper and three lower members, those of the latter on the median line belonging equally to each of the pair.

ACQUIRED QUALITIES.

When an organism has been subjected to abnormal conditions in life it can transmit any peculiarity it may have acquired. This is, however, not always possible, otherwise descendants of men who have lost their arm or leg would be born without the corresponding arm or leg--this shows that some acquired qualities are more easily transmitted than others--although there are cases, as, for instance, a race of dogs without tails has been produced by cutting off the tails of both sexes of the dog, during several generations. "A few years ago," says Haeckel, "a case occurred on an estate near Jena in which, by the careless slamming of a stable-door, the tail of a bull was wrenched off, and the calves begotten by this bull were all born without a tail. This is certainly an exception; but it is very important to note the fact that under certain unknown conditions such violent changes are transmitted in the same manner as many diseases." The transmission of diseases such as consumption, madness, and albinism form examples. Albinoes are those individuals who are distinguished by the absence of coloring matter from their skins; they are of frequent occurrence among men, animals and plants. Among many animals, such as rabbits and mice, albinoes with white fur and red eyes are so much liked that they are propagated. This would be impossible were it not for the law of the transmission of adaptations. Hornless cattle have descended from a single bull born in 1770 of horned parents, but whose absence of horns was the result of some unknown cause.

The law of interrupted or latent transmission, as illustrated in grandchildren who are like the grandparents, but quite unlike the parents. Animals often resume a form which have not existed for many generations. One of the most remarkable instances of this kind of reversion, or "atavism," is the fact that in some horses there sometimes appear singular dark stripes similar to those of the zebra, quagga, and other wild species of African horse.

Nutrition directly modifies adaptation, as is well illustrated by animals which have been bred for domestic or other purposes. If a farmer is breeding for fine wool he gives much different food to the sheep than he would if he wished to obtain flesh or an abundance of fat. Even the bodily form of man is quite different according to its nutrition. Food containing much nitrogen produces little fat, that containing little nitrogen produces a great deal of fat. People who by means of Banting's system, at present so popular, wish to become thin, eat only meat and eggs--no bread, no potatoes.

Man can breed for milk in cattle, for feathers in pigeons, for colored flowers in plants, and, in fact, for almost any desirable quality.

GEOLOGICAL RECORD.

_The Geological Record_ (palæontology) furnishes weighty evidence of man's descent; for the circumstantial evidence derived from this source is written without the possibility of a mistake, with no chance of error, on the stratified rocks. It is true that the geological record must be incomplete, because it can only preserve remains found in certain favorable localities, and under particular conditions; that this valuable record must be destroyed by processes of denudation, and obliterated by processes of metamorphosis, it cannot be doubted. "Beds of rock of any thickness, crammed full of organic remains, may yet," says Huxley, "by the percolation of water through them, or the influence of subterranean heat (if they descend far enough toward the centre of the earth), lose all trace of these remains, and present the appearance of beds of rock formed under conditions in which there was no trace of living forms. Such metamorphic rocks occur in formations of all ages; and we know with perfect certainty, when they do appear, that they have contained organic remains, and that those remains have been absolutely obliterated." If we look at the geological record, we find:

THE FIRST EPOCH.--_The Archilithic_, or Primordial Epoch, constitutes the _Age of Skull-less Animals and Sea-weed Forests_, and is made up of the Laurentian, Cambrian, and Silurian Period.

THE SECOND EPOCH.--_The Palæolithic_, or Primary Epoch, constitutes the _Age of Fishes and Fern Forests_, and is made up of the Devonian, Coal, and Permian Period.

THE THIRD EPOCH.--_The Mesolithic_, or Secondary Epoch, constitutes the _Age of Reptiles and Pine Forests, Coniferæ_, and is made up of the Triassic, Jurassic, and Chalk Period.

THE FOURTH EPOCH.--_The Cænolithic_, or Tertiary Epoch, constitutes the _Age of Mammals and Leaf Forests_, and is made up of the Eocene, Miocene, and Phocene Period.

THE FIFTH EPOCH.--The _Anthropolithic_, or Quaternary Epoch, constitutes the _Age of Man and Cultivated Forests,_ and is made up of the Glacial and Postglacial Period, and the Period of Culture.

During the archilithic epoch the inhabitants of our planet, as has been already stated, consisted of skull-less animals, or aquatic forms. No remains of terrestrial animals or plants, dated from this period, have as yet been found.

The archilithic period was longer than the whole long period between the close of the archilithic and the present time; for if the total thickness of all sedimentary strata be estimated as about one hundred and thirty thousand feet, then seventy thousand feet belong to this epoch. It was during this epoch that the little mass of protoplasm, which has been so often spoken of, came into existence.

It has been stated above that palæontology is quite deficient. This is not only true of the record, but of the lack as yet of sufficient investigations. The greatest fields of investigation in this department have never been explored. The whole of the petrifactions accurately known do not probably amount to a hundredth part of those which, by more elaborate explorations, are yet to be discovered. The most ancient of all distinctly preserved petrifactions is the Eozoon Canadense, which was found in the lowest Laurentian strata in the Ottawa formation.

Probably no discovery in palæontology ranks higher than the discovery of the descendants of the horse. The horse, for example, as far as his limbs and teeth go, differs far more from extant graminivora than man differs from the ape. Had not fossil ungulates been found, which demonstrate the common origin of the horse with didactyles and multidactyles, some would have deemed the horse a special miraculous creation. But now the links are complete, and the descent of the horse is found to follow exactly what the doctrine of evolution could have predicted.

ONTOGENY.

It has been stated that the palæontological record is quite incomplete, owing to many facts, some of which have been mentioned; fortunately, the history of the development of the organic individual, or ontogeny, comes in to fill up many deficiencies.

Ontogeny is a repetition of the principal forms through which the respective individuals have passed from the beginning of their tribe, and its great advantage is that it reveals a field of information which it was impossible for the rocks to retain; for the petrification of the ancient ancestors of all the different animal and vegetable species, which were soft, tender bodies, was not possible.

The annexed plate illustrates the dog, rabbit, and man in their first stages of development. Illustrations of a fish, an amphibious animal, a reptile, a bird, or any mammal, could also be given; for all vertebrate animals of the most different classes, in their early stages of development, cannot be distinguished, and the nearer the animal approaches man in the ascending scale, the longer does this similarity continue to exist--when reptiles and birds are distinctly different from mammals, the dog and the man are almost identical.

The gill-arches of the fish exist in man, in dogs, in fowls, in reptiles, and in other vertebrate animals during the first stages of their development. Man also possesses, in his first stages, a real tail, as well as his nearest kindred--the tailless apes (orang-outang, chimpanzee, gorilla), and vertebrate animals in general. The tail, as has been stated, man still retains, though hidden as a rudiment.