THE SECOND EPOCH.--_The Palaeolithic_, or Primary Epoch, const.i.tutes 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, const.i.tutes the _Age of Reptiles and Pine Forests, Coniferae_, and is made up of the Tria.s.sic, Jura.s.sic, and Chalk Period.

THE FOURTH EPOCH.--_The Caenolithic_, or Tertiary Epoch, const.i.tutes 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, const.i.tutes 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 ma.s.s of protoplasm, which has been so often spoken of, came into existence.

It has been stated above that palaeontology 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 palaeontology 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 palaeontological 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 repet.i.tion of the princ.i.p.al forms through which the respective individuals have pa.s.sed 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 ill.u.s.trates the dog, rabbit, and man in their first stages of development. Ill.u.s.trations 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 cla.s.ses, 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.

[Ill.u.s.tration: FIG. I.--Human Embryo.--_Ecker._]

[Ill.u.s.tration: FIG. II.--Embryo of Dog.--_Bischoff._]

[Ill.u.s.tration: FIG. III.--Dog Embryo.--_Huxley._]

[Ill.u.s.tration: FIGS. IV, V, and VI.--Embryo of Rabbit in three stages of development.--_Haeckel._]

[Ill.u.s.tration: FIGS. VII, VIII, and IX.--Embryo of Man in three stages of development.--_Haeckel._ _v_, fore brain; _z_, twix brain; _m_, middle brain; _h_, hind brain; _n_, after brain; _r_, spinal marrow; _e_, nose; _a_, eye; _o_, ear; _k_, gillarches; _g_, heart; _w_, vertebral column; _f_, fore limbs; _b_, hind limbs; _s_, tail.]

"Man presents in his earliest stages of embryonic growth, a skeleton of cartilage, like that of the lamprey; also, five origins of the aorta and five slits on the neck, like the _lamprey_ and the _shark_. Later, he has but four aortic origins, and a heart now divided into two chambers, like _bony fishes_; the optic lobes of his brain also having a very fish-like predominance in size. Three chambers of the heart and three aortic origins follow, presenting a condition permanent in the _batrachia_; then two origins with enlarged hemispheres of the brain, as in _reptiles_. Four heart chambers and one aortic root on each side, with slight development of the cerebellum, agree with the characters of the _crocodiles_, and immediately present the special mammalian conditions, single aortic root, and the full development of the cerebellum. Later comes that of the cerebrum, also in its higher mammalian or human traits." At no time in the development of the egg, save at the start, do the embryos of the various vertebra a.s.sume the _exact_ or _entire_ characteristics of one another, but they a.s.similate so closely that it requires the eye of the expert to distinguish them; and, as has already been stated, the more closely an animal resembles another, the longer and the more intimately do their embryos resemble one another; so that, for example, the embryo of the snake and of a lizard remain like one another longer than do those of a snake and of a bird; and the embryo of a dog and of a cat remain like one another for a far longer period than do those of a dog and a bird, or a dog and an opossum, or even those of a dog and a monkey.

Surely it must be admitted that the short brief history given by the development of the egg, is far more wonderful than phylogeny or the long and slow history of the development of the tribe, which has taken thousands of years. Compare this time with the time required for the development of the smallest mammals--the harvest mice which develops in three weeks, or the smallest of all birds, the humming-bird, which quits the egg on the twelfth day, or with man who pa.s.ses through the whole course of his development in forty weeks, or with the rhinoceros who requires 1-1/2 years, or the elephant who requires ninety weeks. How insignificant are these various periods to the long period originally required; yet in these short periods the whole phylogeny is run through in the ontogeny or the history of the development of the egg.

THE ATTRIBUTES OF MAN.

We must now consider briefly some of the attributes of man, and see if he really possesses attributes which are in no inferior degree possessed by animals. Before proceeding directly to the consideration of the attributes of man, it will be best to show the correlation that exists between what are called man's vital forces and the physical forces of nature. To do this let us choose three forms of its manifestation: these shall be heat evolved within the body; muscular energy or motion; and lastly, nervous energy or that form of force which, on the one hand, stimulates a muscle to contract, and on the other appears in forms called mental. It will not take any extensive argument to demonstrate that the heat of the body does not differ from heat from any other source. It is known that the food taken into the body contains potential energy, which is capable of being in part converted into actual heat by oxidation; and since we know that the food taken into the body is oxidized by the oxygen of the air supplied by the lungs, the heat of the body must be due to the slow oxidation of the carbon, perhaps also hydrogen, sulphur, and phosphorus in the food. Now since this so-called vital heat is developed by oxidation, is recognized by the same tests and applied to the same purposes as any other heat, it is as truly correlated to the other forces as when it has a purely physical origin.

The amoeboid activity of a white blood corpuscle is stimulated within certain limits by heat. Hatching of eggs and the germination of seeds may be likewise hastened or r.e.t.a.r.ded by access or deprivation of heat.

It was considerations such as these which led to the doctrine of correlation of the vital and physical forces.

With respect to the muscular force exerted by an animal, it was supposed that it was created by the animal. Dr. Frankland[36] says to this: "An animal can no more generate an amount of force capable of moving a grain of sand, than a stone can fall upwards or a locomotive drive a train without fuel." As the amount of CO{2} exhaled by the lungs is increased in the exact ratio of work done by the muscle, it cannot be doubted that the actual force of the muscle is due to the converted potential energy of the food. Since every exertion of a muscle and nerves involves the death and decay of those tissues to a certain extent, as shown by the excretions, Prof. Orton[37] has been led to say: "An animal begins to die the moment it begins to live." "A muscle," says Barker,[38] "is like a steam-engine, is a machine for converting the potential energy of carbon into motion; but unlike a steam-engine, the muscle accomplishes this conversion directly, the energy not pa.s.sing through the intermediate stages of heat. For this reason the muscle is the most economical producer of mechanical force known." The muscles which give the downward stroke of the wing of a bird are fastened to the breastbone, and their power in proportion to the weight of the bird is as 10,000 to 1. This great power is needed, for the air is 770 times lighter than water; the hawk being able to travel 150 miles an hour.

The last of the so-called vital forces under consideration, is that produced by the nerves and nervous centres. Barker says: "In the nerve which stimulates a muscle to contract, this force is undeniably motion, since it is propagated along this nerve from one extremity to the other." This force has been likened unto electricity, the gray or cellular matter being the battery, the white or fibrous matter the conductors. Du Bois Reymond[39] has demonstrated that this force is not electricity, though by showing that its velocity is only ninety-seven feet a second. The velocity varies, though, in different animals; it is, according to Prof. Orton,[40] "more rapid in warm-blooded than in cold-blooded animals, being nearly twice as fast in man as in the frog."

Wheatstone, by his method, gives the velocity of electricity in copper wire at 62,000 geographical miles per second; but as neither Fizeau, Gould, Gonnelle and others could arrive at the same result, the method was shown to be incorrect, and it remained for Dr. Siemen[41] to discover the true method, which gives the velocity just one-half that of Wheatstone's estimate, or 31,000 geographical miles per second. In the opinion of Bence Jones, the propagation of a nervous impulse is a sort "of successive molecular polarization, like magnetism." But that this agent is a force as a.n.a.logous to electricity as is magnetism, is shown not only by the fact that the transmission of electricity along a nerve will cause the contraction of a muscle to which it leads, but also by the important fact discovered by Marshall, that the contraction of a muscle is excited by diminishing its normal electrical current,[42] a result which could take place only with a stimulus, says Barker, "closely allied to electricity. Nerve force must therefore be trans.m.u.ted potential energy." Prof. Huxley says,[43] "the results of recent inquiries into the structure of the nervous system of animals, converge toward the conclusion that the nerve-fibres which we have hitherto regarded as ultimate elements of nervous tissue, are not such, but are simply the visible aggregations of vastly more attenuated filaments, the diameter of which dwindles down to the limits of our present microscopic vision, greatly as these have been extended by modern improvements of the microscope; and that a nerve is, in its essence, nothing but a linear tract of specially modified protoplasm between two points of an organism, one of which is able to affect the other by means of the communication so established. Hence it is conceivable that even the simplest living being may possess a nervous system."

Herbert Spencer[44] says all direct and indirect evidence "justifies us in concluding that the nervous system consists of _one_ kind of matter.

In the gray tissue this matter exists in ma.s.ses containing _corpuscles_, which are soft and have granules dispersed through them, and which, besides being thus unstably composed, are placed so as to be liable to disturbances to the greatest degree. In the white tissue this matter is collected together in extremely slender _threads_ that are denser, that are uniform in texture, and that are shielded in an unusual manner from disturbing forces, except at their two extremities."

The last consideration is that form of force (thought power) which appears in manifestations called mental. It must be noticed at the outset, that every external manifestation of thought force is a muscular one, as a word spoken or written, a gesture, or an expression of the face always takes place; hence this force must be intimately correlated to nerve force. It is very certain, then, that thought force is capable in external manifestations of converting itself into actual motion. But here the question arises, can it be manifested inwardly without such a transformation of energy? Or is the evolution of thought entirely independent of the matter of the brain?

This question can be answered by actual experiment, strange as it may appear. Experiments have demonstrated that any change of temperature within the skull was soonest manifested externally in that depression which exists just above the occipital protuberance. Here Lombard[45]

fastened to the head at this point two little bars, one made of bis.m.u.th, the other of an alloy of antimony and zinc, which were connected with a delicate galvanometer;[46] to neutralize the result of a gradual rise of temperature over the whole body, a second pair of bars, reversed in direction, was attached to the leg or arm, so that if a like increase of heat came to both, the electricity developed by one would be neutralized by the other, and no effect would be produced by the needle unless only one was affected. By long practice it was ascertained that a mental torpor could be induced, lasting for hours, in which the needle remained stationary. But let a person knock on the door outside of the room, or speak a single word, even though the experimenter remained absolutely pa.s.sive, the reception of the intelligence caused the needle to swing twenty degrees. "In explanation of this production of heat," says Barker,[47] "the a.n.a.logy of the muscle at once suggests itself. No conversion of energy is complete, and as the heat of muscular action represents force which has escaped conversion into motion, so the heat evolved during the reception of an idea is energy which has escaped conversion into thought, from precisely the same cause." Dr. Lombard's experiments have shown that the amount of heat developed by the recitation to one's self of emotional poetry, was in every case less when recitation was oral; this is of course accounted for by the muscular expression. Chemistry teaches that thought-force, like muscle-force, comes from the food, and demonstrates that the force evolved by the brain, like that produced by the muscle, comes not from the disintegration of its own tissue, but is the converted energy of burning carbon.[48] "Can we longer doubt," says Barker,[49] "that the brain too, is a machine for the conversion of energy? Can we longer refuse to believe that even thought force is in some mysterious way correlated to the other natural forces? and this even in the face of the fact that it has never yet been measured.[50] Have we not a right to ask 'why a special force (vital force) should be needed to effect the transformation of physical forces into those modes of energy which are active in the manifestation of living beings, while no peculiar force is deemed necessary to effect the transformation of one mode of physical force into any other mode of physical force?"

Richard Owen says:[51] "In the endeavor to clearly comprehend and explain the functions of the combination of forces called 'brain,' the physiologist is hindered and troubled by the views of the nature of those cerebral forces which the needs of dogmatic theology have imposed on mankind. * * * Religion, pure and undefiled, can best answer how far it is righteous or just to charge a neighbor with being unsound in his principles who holds the term 'life' to be a sound expressing the sum of living phenomena, and who maintains these phenomena to be modes of force into which other forms of force have pa.s.sed from potential to active states, and reciprocally, through the agency of the sums or combinations of forces impressing the mind with the ideas signified by the terms 'monad,' 'moss,' 'plant,' or 'animal.'"

We have now shown that the very forces which give vent to the attributes of man, are correlated to the physical forces. Let us now consider his attributes as manifested by his mental powers. There is no doubt the difference between the mental faculties of the ape and that of the lowest savage, who cannot express any number higher than four and who uses hardly any abstract terms for common objects or for the affections,[52] is still very great and would still be great, says Darwin, "even if one of the higher apes had been improved or civilized as much as a dog has been in comparison with its parent form, the wolf or jackal." But when we examine the interval of mental power between one of the lowest fishes, as a lamprey or a lancelet, and one of the higher apes, and recognize the fact that this interval is filled up by numberless gradations, it does not become so difficult to understand the interval between an ape and man, which is not by far so great. As in finding out what is peculiar to a living body in distinction to a body not living, we found it absurd to take man as the perfection of the animal scale--the microscopic monad possessing life as well as him--so in the case of man's mental attributes, which have always been increasing, always perfecting, since the first genuine man came into existence, it would be equally absurd to compare the intellectual man of to-day with an ape to see what attributes he possesses which the ape does not possess; but if we go down in the scale and compare the savage with the ape, the difficulty is not by far so great. It will be found on close examination, though, that man and the higher animals, especially the primates, have many instincts in common. "All," says Darwin, "have the same senses, intuitions and sensations; similar pa.s.sions, affections, and emotions; even the more complex ones, such as jealousy, suspicion, emulation, grat.i.tude and magnanimity; they practice deceit and are revengeful; they are sometimes susceptible to ridicule and even have a sense of humor; they feel wonder and curiosity; they possess the same faculties of imitation, attention, deliberation, choice, memory, imagination, the a.s.sociation of ideas, and reason, though in very different degrees. The individuals of the same species graduate in intellect from absolute imbecility to high excellence; they are also liable to insanity, though far less often than in the case of man."[53] Nevertheless, in the face of these facts, many authors have insisted that man is divided by an inseparable barrier from all the lower animals in his mental faculties. It only shows the improper or imperfect consideration of the subject they have under discussion.

It may be thought at first that some of the mental attributes mentioned above are not possessed by animals. I therefore will briefly consider a few of the more complex ones. We can dismiss the consideration of such attributes as happiness, terror, suspicion, courage, timidity, jealousy, shame, and wonder, as well-known attributes. _Curiosity_ in animals is often observed. An instance mentioned by Brehm will serve to ill.u.s.trate: Brehm gives a curious account of the instinctive dread which his monkeys exhibited for snakes; but their curiosity was so great that they could not desist from occasionally satiating their horror in a most human fashion, by lifting up the lid of the box in which the snakes were kept.

_Imitation_ is also found among the action of animals, especially among monkeys, which are well known to be ridiculous mockers.

It is unnecessary to refer to the faculty of attention, as it is common to almost all animals, and the same may be said of memory as for persons or places.

One would hesitate to believe an animal possesses _imagination_, but such is the case. Dreaming, it will be admitted, gives us the best notion of this power. Now as dogs, cats, horses, and probably all the higher animals, even birds, have vivid dreams--this is shown by their movements and the sounds uttered--"we must admit," says Darwin, "they possess some power of imagination. There must be something special which causes dogs to howl in the night, and especially during moonlight, in that remarkable and melancholy manner, called baying. All dogs do not do so; and, according to Housyeau,[54] they do not look at the moon, but at some fixed point near the horizon. Housyeau thinks that their imaginations are disturbed by the vague outlines of the surrounding objects, and conjure up before them fantastic images; if this be so, their feelings may almost be called superst.i.tious."

The next mental faculty is _reason_, which stands at the summit; but still there are few persons who will deny that animals possess some power of reasoning. A few ill.u.s.trations will be all that is necessary to satisfy the inquiring mind on this point. Reugger, a most careful observer, states that when he first gave eggs to his monkey in Paraguay they smashed them, and thus lost much of their contents; afterward they gently hit one end against some hard body, and picked off the bits of sh.e.l.l with their fingers. After cutting themselves _once_ with any sharp tool, they would not touch it again, or would handle it with the greatest caution. Lumps of sugar were often given them, wrapped up in paper; and Reugger sometimes put a live wasp in the paper, so that in hastily unfolding it they got stung; after this had _once_ happened, they afterward first held the packet to their ears to detect any movement within.

The following cases relating to dogs are described by Darwin: Mr.

Colquhoun winged two wild ducks, which fell on the farther side of a stream; his retriever tried to bring over both at once, but could not succeed; she then, though never before known to ruffle a feather, deliberately killed one, brought over the other, and returned for the dead bird. Colonel Hutchinson relates that two partridges were shot at once--one being killed, the other wounded; the latter ran away, and was caught by the retriever, who, on her return, came across the dead bird; "she stopped, evidently greatly puzzled, and after one or two trials, finding she could not take it up without permitting the escape of the winged bird, she considered a moment, then deliberately murdered it by giving it a severe crunch, and afterward brought away both together.

This was the only known instance of her ever having wilfully injured any game. Here we have reason, though not quite perfect; for the retriever might have brought the wounded bird first, and then returned for the dead one, as in the case of the two wild ducks. I give the above cases as resting on the evidence of two independent witnesses; and because in both instances the retrievers, after deliberation, broke through a habit which was inherited by them (that of not killing the game retrieved), and because they show how strong their reasoning faculty must have been to overcome a fixed habit."[55]

It has often been said that no animal uses any tool, but this can be so easily refuted on reflection, that it is hardly worth while considering; for ill.u.s.tration, though, the chimpanzee in a state of nature cracks nuts with a stone; Darwin saw a young orang put a stick in a crevice, slip his hand to the other end, and use it in a proper manner as a lever. The baboons in Abyssinia descend in troops from the mountains to plunder fields, and when they meet troops of another species a fight ensues. They commence by rolling great stones at their enemies, as they often do when attacked with fire-arms.

The Duke of Argyll remarks that the fashioning of an implement for a special purpose is absolutely peculiar to man; and he considers this forms an immeasurable gulf between him and the brutes. "This is no doubt," says Darwin, "a very important distinction; but there appears to me much truth in Sir J. Lubbock's suggestion,[56] that when primeval man first used flint-stones for any purpose, he would have accidentally splintered them, and would then have used the sharp fragments. From this step it would be a small one to break the flints on purpose, and not a very wide step to fashion them rudely. The later advance, however, may have taken long ages, if we may judge by the immense interval of time which elapsed before the men of the neolithic period took to grinding and polishing their stone tools. In breaking the flints, as Sir J.

Lubbock likewise remarks, sparks would have been emitted, and in grinding them heat would have been evolved; thus the two usual methods of 'obtaining fire may have originated.' The nature of fire would have been known in many volcanic regions where lava occasionally flows through forests."

It becomes a difficult task to determine how far animals exhibit any traces of such high faculties as _abstraction_, _general conception_, _self-consciousness_, _mental individuality_. There can be no doubt, if the mental faculties of an animal can be improved, that the higher complex faculties such as abstraction and self-consciousness have developed from a combination of the simpler ones; this seems to be well ill.u.s.trated in the young child, as such faculties are developed by imperceptible degrees. These high faculties are very sparingly possessed by the savage; as Buchner[57] has remarked, how little can the hard-worked wife of a degraded Australian savage, who uses very few abstract words and cannot count above four, exert her self-consciousness or reflect on the nature of her own existence. If there exist a cla.s.s of people so inferior in their mental faculties as these, it is not difficult for us to understand how the educated animal who possesses memory, attention, a.s.sociation, and even some imagination and reason, can become capable of abstraction, &c., in an inferior degree even to the savage. It certainly cannot be doubted that an animal possesses mental individuality--as when a master returns to a dog which he has not seen for years, and the dog recognizes him at once.

One of the chief distinctions between man and animals is the faculty of language. Let us look at this for a moment. "The essential differences,"

says Prof. Whitney, "which separate man's means of communication in kind as well as degree from that of the other animals is that, while the latter is instinctive, the former is in all its parts arbitrary and conventional. No man can become possessed of any language without learning it; no animal (that we know of) has any expression which he learns, which is not the direct gift of nature to him." Any child of parents living in a foreign country grows up to speak the foreign speech, unless carefully guarded from doing so; or it speaks both this and the tongue of its parent with equal readiness. A child must learn to observe and distinguish before speech is possible, and every child begins to know things by their name before he begins to call them. "If it were not for the added push," says Prof. Whitney, "given by the desire of communication, the great and wonderful power of the human soul would never move in this particular direction; but when this leads the way, all the rest follows." No philologist now supposes that any language has been deliberately invented; it has been slowly and unconsciously developed by many steps.

There can be no question that language owes its origin to the imitation and modification of various natural sounds, the voices of other animals, and man's own instinctive cries, aided by signs and gestures; and this is the opinion of Max Muller. And Prof. Whitney remarks that "spoken language began, we may say, when a cry of pain, formally wrung out by real suffering, and seen to be understood and sympathized with, was repeated in imitation, no longer as a mere instinctive utterance, but for the purpose of intimating to another." Darwin says that "the early progenitor of man probably first used his voice in producing true musical cadences, that is, in singing, as do some gibbon-apes at the present day. It is therefore probable that the imitation of musical cries by articulate sounds may have given rise to words expressive of very complex emotions."

The nearest approach to language are the sounds uttered by birds. All that sing exert their power instinctively, but the actual song, and even the call notes, are learned from their parents or foster-parents. These sounds are no more innate than language is in man, as has been proved by Davies Barrington.[58] The first attempt to sing "may be compared to the imperfect endeavor in a child to babble." Prof. Whitney says, if the last transition forms of man "could be restored, we should find the transition forms toward our speech to be, not at all a minor provision of natural articulate signs, but an inferior system of conventional signs, in tone, gesture, and grimace. As between these three natural means of expression, it is simply by a kind of process of natural selection and survival of the fittest that the voice has gained the upper hand, and come to be so much the most prominent that we give the name of language (tonguiness) to all expression." A single utterance or two at first had to do the duty of a whole clause; afterward man learned to piece together parts of speech, and thus arose sentences.

Although no language, as has already been said, has been deliberately invented, "still each word may not be unfitly compared to an invention; it has its own place, mode, and circ.u.mstances of devisal, its preparation in the previous habits of speech, its influence in determining the after progress of speech development; but every language in the gross is an inst.i.tution, on which scores or hundreds of generations and unnumbered thousands of individual workers have labored."[59]