first rose to a flourishing condition on the sh.o.r.es of the Mediterranean. The former area of the distribution of this species is expressed by the name of "Indo-Atlantic" species, whereas at present it is spread over the whole earth, and is overcoming most of the other species in the struggle for existence. In bodily as well as in mental qualities, no other human species can equal the Mediterranean. This species alone (with the exception of the Mongolian) has had an actual history; it alone has attained to that degree of civilization which seems to raise man above the rest of nature.

The characteristics which distinguish the Mediterranean from the other species of the race are well known. The chief of the external features is the light colour of the skin, which however exhibits all shades, from pure white or reddish white, through yellow or yellowish brown to dark brown or even black brown. The growth of the hair is generally strong, the hair of the head more or less curly, the hair of the beard stronger than in any of the other species. The form of the skull shows a great development in breadth; medium heads predominate upon the whole, but long and short heads are also widely distributed. It is only in this one species of men that the body as a whole attains that symmetry in all parts, and that equal development, which we call the type of perfect human beauty. The languages of all the races of this species can by no means be traced to a single common primaeval language; we must at least a.s.sume four radically different primaeval languages. In accordance with this we must also a.s.sume within this one species four different races, which are only connected at their root. Two of these races, the Basques and Caucasians, now exist only as small remnants. The Basques, which in earlier times peopled the whole of Spain and the south of France, now inhabit but a narrow tract of land on the northern coast of Spain, on the Bay of Biscay. The remnant of the Caucasian race (the Daghestans, Tscherca.s.sians, Mingrelians, and Georgians) are now confined to the districts of Mount Caucasus. The language of the Caucasians as well as that of the Basques is entirely peculiar, and can be traced neither to the Semitic nor to the Indo-Germanic primaeval languages.

Even the languages of the two princ.i.p.al races of the Mediterranean species-the Semitic and Indo-Germanic-cannot be traced to a common origin, and consequently these two races must have separated at a very early period. Semites and Indo-Germani are descended from different ape-like men. The _Semitic_ race likewise separated at a very early period into two diverging branches, namely, into the _Egyptian_ and _Arabic_ branches. The _Egyptian_, or _African_ branch, the _Dyssemites_-which sometimes under the name of Hamites are entirely separated from the Semites-embraces the large group of Berbers, who occupy the whole of north Africa, and in earlier times also peopled the Canary Islands, and, finally, also the group of the Ethiopians, the Bedsha, Galla, Danakil, Somali, and other tribes which occupy all the north-eastern sh.o.r.es of Africa as far as the equator. The _Arabic_, or _Asiatic_ branch, that is, the _Eusemites_, also called Semites in a narrow sense, embrace the inhabitants of the large Arabian peninsula, the primaeval family of genuine Arabians ("primaeval type of the Semites"), and also the most highly developed Semitic groups, the Jews, or Hebrews, and the Aramaeans-the Syrians and Chaldaeans. A colony of the southern Arabs (the Himjarites), which crossed the Straits of Bab-el-Mandeb, has peopled Abyssinia.

Lastly, the Indo-Germanic race, which has far surpa.s.sed all the other races of men in mental development, separated at a very early period, like the Semitic, into two diverging branches, the _Ario-Romaic_ and the _Slavo-Germanic_ branches. Out of the former arose on the one hand the _Arians_ (Indians and Iranians), on the other the _Graeco-Roman_ (Greeks and Albanians, Italians and Kelts). Out of the Slavo-Germanic branch were developed on the one hand the _Slavonians_ (Russian, Bulgarian, Tchec, and Baltic tribes), on the other the _Germani_ (Scandinavians and Germans, Netherlanders and Anglo-Saxons). August Schleicher has explained, in a very clear genealogical form, how the further ramifications of the Indo-Germanic race may be accurately traced in detail on the basis of comparative philology.(6) (Compare p. 331.)

The total number of human individuals at present amounts to between 1,300 and 1,400 millions. In our Tabular Survey (p. 333) 1,350 millions has been a.s.sumed as the mean number. According to an approximate estimate, as far as such a thing is possible, 1,200 millions of these are straight-haired men, only about 150 millions woolly-haired. The most highly developed species, Mongols and Mediterranese, far surpa.s.s all the other human species in numbers of individuals, for each of them alone comprises about 550 millions. (Compare Friederich Muller's Ethnography, p. 30.) Of course the relative number of the twelve species fluctuates every year, and that too according to the law developed by Darwin, that in the struggle for life the more highly developed, the more favoured and larger groups of forms, possess the positive inclination and the certain tendency to spread more and more at the expense of the lower, more backward, and smaller groups. Thus the Mediterranean species, and within it the Indo-Germanic, have by means of the higher development of their brain surpa.s.sed all the other races and species in the struggle for life, and have already spread the net of their dominion over the whole globe. It is only the Mongolian species which can at all successfully, at least in certain respects, compete with the Mediterranean. Within the tropical regions, Negroes, Kaffres, and Nubians, as also the Malays and Dravidas, are in some measure protected against the encroachments of the Indo-Germanic tribes by their being better adapted for a hot climate; the case of the arctic tribes of the polar regions is similar. But the other races, which as it is are very much diminished in number, will sooner or later completely succ.u.mb in the struggle for existence to the superiority of the Mediterranean races. The American and Australian tribes are even now fast approaching their complete extinction, and the same may be said of the Papuans and Hottentots.

In now turning to the equally interesting and difficult question of the relative _connection_, _migration_, and _primaeval home_ of the twelve species of men, I must premise the remark that, in the present state of our anthropological knowledge, any answer to this question must be regarded only as a provisional hypothesis. This is much the same as with any genealogical hypothesis which we may form of the origin of kindred animal and vegetable species, on the basis of the "Natural System." But the necessary uncertainty of these special hypotheses of descent, in no way shakes the absolute certainty of the general theory of descent. Man, we may feel certain, is descended from Catarrhini, or narrow-nosed apes, whether we agree with the polyphylites, and suppose each human species, in its primaeval home, to have originated out of a special kind of ape; or whether, agreeing with the monophylites, we suppose that all the human species arose only by differentiation from a single species of primaeval man (h.o.m.o primigenius).

For many and weighty reasons we hold the monophyletic hypothesis to be the more correct, and we therefore a.s.sume a _single primaeval home_ for mankind, where he developed out of a long since extinct anthropoid species of ape. Of the five now existing continents, neither Australia, nor America, nor Europe can have been this primaeval home, or the so-called "Paradise," the "cradle of the human race." Most circ.u.mstances indicate southern Asia as the locality in question.

Besides southern Asia, the only other of the now existing continents which might be viewed in this light is Africa. But there are a number of circ.u.mstances (especially chorological facts) which suggest that the primaeval home of man was a continent now sunk below the surface of the Indian Ocean, which extended along the south of Asia, as it is at present (and probably in direct connection with it), towards the east, as far as further India and the Sunda Islands; towards the west, as far as Madagascar and the south-eastern sh.o.r.es of Africa. We have already mentioned that many facts in animal and vegetable geography render the former existence of such a south Indian continent very probable.

(Compare vol. i. p. 361.) Sclater has given this continent the name of Lemuria, from the Semi-apes which were characteristic of it. By a.s.suming this Lemuria to have been man's primaeval home, we greatly facilitate the explanation of the geographical distribution of the human species by migration. (Compare the Table of Migrations XV., and its explanation at the end.)

We as yet know of no fossil remains of the hypothetical primaeval man (h.o.m.o primigenius) who developed out of anthropoid apes during the tertiary period, either in Lemuria or in southern Asia, or possibly in Africa. But considering the extraordinary resemblance between the lowest woolly-haired men, and the highest man-like apes, which still exist at the present day, it requires but a slight stretch of the imagination to conceive an intermediate form connecting the two, and to see in it an approximate likeness to the supposed primaeval men, or ape-like men. The form of their skull was probably very long, with slanting teeth; their hair woolly; the colour of their skin dark, of a brownish tint. The hair covering the whole body was probably thicker than in any of the still living human species; their arms comparatively longer and stronger; their legs, on the other hand, knock-kneed, shorter and thinner, with entirely undeveloped calves; their walk but half erect.

This ape-like man very probably did not as yet possess an actual human language, that is, an articulate language of ideas. Human speech, as has already been remarked, most likely originated after the divergence of the primaeval species of men into different species. The number of primaeval languages is, however, considerably larger than the number of the species of men above discussed. For philologists have hitherto not been able to trace the four primaeval languages of the Mediterranean species, namely, the Basque, Caucasian, Semitic, and Indo-Germanic to a single primaeval language. As little can the different Negro languages be derived from a common primaeval language; hence both these species, Mediterranean and Negro, are certainly _polyglottonic_, that is, their respective languages originated after the divergence of the speechless primary species into several races had already taken place. Perhaps the Mongols, the Arctic and American tribes, are likewise polyglottonic. The Malayan species is, however, _monoglottonic_; all the Polynesian and Sundanesian dialects and languages can be derived from a common, long since extinct primaeval language, which is not related to any other language on earth. All the other human species, Nubians, Dravidas, Australians, Papuans, Hottentots, and Kaffres are likewise monoglottonic. (Compare p. 333.)

Out of speechless primaeval man, whom we consider as the common primary species of all the others, there developed in the first place-probably by natural selection-various species of men unknown to us, and now long since extinct, and who still remained at the stage of speechless ape-men (Alalus, or Pithecanthropus). Two of these species, a woolly-haired and a straight-haired, which were most strongly divergent, and consequently overpowered the others in the struggle for life, became the primary forms of the other remaining human species.

The main branch of woolly-haired men (Ulotrichi) at first spread only over the southern hemisphere, and then emigrated partly eastwards, partly westwards. Remnants of the eastern branch are the Papuans in New Guinea and Melanesia, who in earlier times were diffused much further west (in further India and Sundanesia), and it was not until a late period that they were driven eastwards by the Malays. The Hottentots are the but little changed remnants of the western branch; they immigrated to their present home from the north-east. It was perhaps during this migration that the two nearly related species of Caffres and Negroes branched off from them; but it may be that they owe their origin to a peculiar branch of ape-like men.

The second main branch of primaeval straight-haired men (Lissotrichi), which is more capable of development, has probably left a but little changed remnant of its common primary form-which migrated to the south-east-in the ape-like natives of Australia. Probably very closely related to these latter are the South Asiatic _primaeval Malays_, or _Promalays_, which name we have previously given to the extinct, hypothetical primary form of the other six human species. Out of this unknown common primary form there seem to have arisen three diverging branches, namely, the true Malays, the Mongols, and the Euplocomi; the first spread to the east, the second to the north, and the third westwards.

The primaeval home, or the "Centre of Creation," of the Malays must be looked for in the south-eastern part of the Asiatic continent, or possibly in the more extensive continent which existed at the time when further India was directly connected with the Sunda Archipelago and eastern Lemuria. From thence the Malays spread towards the south-east, over the Sunda Archipelago as far as Borneo, then wandered, driving the Papuans before them, eastwards towards the Samoa and Tonga Islands, and thence gradually diffused over the whole of the islands of the southern Pacific, to the Sandwich Islands in the north, the Mangareva in the east, and New Zealand in the south. A single branch of the Malayan tribe was driven far westwards and peopled Madagascar.

The second main branch of primaeval Malays, that is, the Mongols, at first also spread in Southern Asia, and, radiating to the east, north, and north-west, gradually peopled the greater part of the Asiatic continent. Of the four princ.i.p.al races of the Mongol species, the Indo-Chinese must perhaps be looked upon as the primary group, out of which at a later period the other Coreo-j.a.panese and Ural-Altaian races developed as diverging branches. The Mongols migrated in many ways from western Asia into Europe, where the species is still represented in northern Russia and Scandinavia by the Fins and Lapps, in Hungary by the kindred Magyars, and in Turkey by the Osmanlis.

PEDIGREE OF SEMITES

Amharites +Moors+ +Jews+ | Tigrites | Samaritans (Hebrews) | Harrarites | | | Phnicians | | | | | | | | | | | | Chaldeans | | -------v------/ | Syrians | ----v-----/ +Abyssinians+ | | | Canaanites Ekilians | | | | (+Palestinese+) | | | ---v---/ | | Himiarites | +Aramaeans+ | | | | | | | | | | | ---v---/ | | | +South+ +North+ ----------v------------/ +Arabians+ +Arabians+ +Primaeval Jews+ | | +North-Semites+ -------v-----------/ | +Arabians+ (+South Semites+) | | | | | ----------------------------------------v-----/ Guanchites +Eusemites+ (+Primaeval Semites+) Schuluhs | Algerians (Semites in a narrow sense) | | Tunese | ------------------------v---/ | | | | | | | | | Tripolitans | ---v---/ | | | | Moroccans ----v----/ | +Tuaric+ | | Cabyles | (+Imoscharh+) | | | | | | --------------v--------------/ | | +Berbers+ (+Amazirh+) | | Gallites | | | | Somalites | | | | | ------------v-------------/ | ---v---/ Bedschites +Libians+ Babylonians +Eusemites+ | | Egyptians | Primaeval | | | | (+Copts+) | Phnicians | a.s.syrians | ----v-----/ | | | | | | +Ethiopians+ | | | | | | | | | | | | | | | | | | | | ------------v----------/ -------v------/ | +Ancient Egyptians+ +Mesopotamians+ | | (extinct) | | | | | | | ------------v-----------------/ | +Hamites+ (+Dyssemites+) | | | ---------------v--------------/ +Semites+

PEDIGREE OF THE INDO-GERMANI

Ancient Prussians +Anglo-Saxons+ +High Germans+ Lithuanians | | Low Germans | | Letts | | | Netherlanders | | | | | | | | | | | | | | | -----v----/ | | ----v---/ | | | | Ancient Saxons | | | | | | -------v-/ | | | +Baltic Races+ ------v----/ | Sorbians, or | Saxons Friesians | Wends | | | | Poles | | | | | | | | ----v----/ | Czecs | | | +Low Germans+ | | | | | | | | | | | | | --v-----------/ | Scandinavians -----v------/ West Sclavonians | | Goths +Germans+ | Russians | | | | | South | | | | | | Sclavonians| | ----v----------------------/ | | | | +Primaeval Germans+ Ancient Britons | | | | | | | ---v---/ | | Ancient Scots | Gauls | South-eastern | | +Romans+ Irish | | | | Sclavonians | | | | | | | | | | | | | | --v-/ | | | | | --v-/ Brittanese | | | | | +Latins+ Gaels | ----v----/ | | | | | | +Sclavonians+ | | | | | | | | | --v--/ ----v-----/ | | | Italians +Kelts+ ------v------/ | | | +Sclavo-Letts+ | | | | | --------v---------/ | | +Italo-Kelts+ --v-----------------/ | +Sclavo-Germans+ +Albanese+ +Greeks+ | | | | | | | | | | ----v-----/ | | +Primaeval Thracians+ | | +Indians+ | | | | +Iranians+ -------v-------/ | | | +Graeco-Romans+ | ---v--/ | | +Arians+ | | | | | -----v----------/ | +Ario-Romans+ | | -------v-------/ +Indo-Germans+

On the other hand, a branch of the Mongols migrated from north-eastern Asia to America, which was probably in earlier times connected with the former continent by a broad isthmus. The Arctic tribes, or Polar men, the Hyperboreans of north-eastern Asia, and the Esquimaux of the extreme north of America, must probably be regarded as an offshoot of this branch, which became peculiarly degenerated by unfavourable conditions of existence. The princ.i.p.al portion of the Mongolian immigrants, however, migrated to the south, and gradually spread over the whole of America, first over the north, later over South America.

The third and most important main branch of primaeval Malays, the curly-haired races, or Euplocomi, have probably left in the Dravidas of Hindostan and Ceylon, that species of man which differs least from the common primary form of the Euplocomi. The princ.i.p.al portion of the latter, namely, the Mediterranean species, migrated from their primaeval home (Hindostan?) westwards, and peopled the sh.o.r.es of the Mediterranean, south-western Asia, north Africa, and Europe. The Nubians, in the north-east of Africa, must perhaps be regarded as an offshoot of the primaeval Semitic tribes, who migrated far across central Africa almost to the western sh.o.r.es. The various branches of the Indo-Germanic race have deviated furthest from the common primary form of ape-like men. During cla.s.sic antiquity and the middle ages, the Romanic branch (the Graeco-Italo-Keltic group), one of the two main branches of the Indo-Germanic species, outstripped all other branches in the career of civilization, but at present the same position is occupied by the Germanic. Its chief representatives are the English and Germans, who are in the present age laying the foundation for a new period of higher mental development, in the recognition and completion of the theory of descent. The recognition of the theory of development and the monistic philosophy based upon it, forms the best criterion for the degree of man's mental development.

SYSTEMATIC SURVEY OF THE TWELVE HUMAN SPECIES.

N.B.-Column A denotes the Average Number of the Population in millions. Column B shows the Degree of the Phyletic Development of the Species, thus Pr = Progressive Diffusion; Co = Comparative Stability; Re = Retrogression and Extinction. Column C denotes the Character of the Primaeval Language; Mn (Monoglottonic) signifies that the Species had one Simple Primaeval Language; Pl (Polyglottonic) a Compound Primaeval Language.

----------------------+--------------------+--------+-------+--------+----------------------------- _Tribe._ | _Human | A. | B. | C. | _Home._ | Species._ | | | | ----------------------+--------------------+--------+-------+--------+-----------------------------

TUFT-HAIRED { | | | +Lophocomi+ { 1. PAPUAN | 2 | Re | Mn { New Guinea and Melanesia, { | | | { Philippine Islands, Malacca (about 2 millions) { 2. HOTTENTOT | 1/20 | Re | Mn { The extreme south of Africa { | | | { (The Cape) | | | FLEECY-HAIRED { 3. KAFFRE | 20 | Pr | Mn { South Africa (between 30 { | | | { S. Lat. and 5 N. Lat.) +Eriocomi+ { 4. NEGRO | 130 | Pr | Pl { Central Africa (between the { | | | { Equator and 30 N. Lat.) (about 150 millions) { | | | | | | { 5. AUSTRALIAN | 1/12 | Re | Mn { Australia { 6. MALAY | 30 | Co | Mn { Malacca, Sundanesia, Polynesia, { | | | { and Madagascar STRAIGHT-HAIRED { | | | +Euthycomi+ { 7. MONGOL | 550 | Pr | Mn? { The greater part of Asia { | | | { and northern Europe (about 600 millions) { 8. ARCTIC | 1/25 | Co | Pl? { The extreme north-east of { MAN | | | { Asia and the extreme north { | | | { of America { 9. AMERICAN | 12 | Re | Mn? { The whole of America with { | | | { the exception of the extreme { | | | { north | | | { 10. DRAVIDAS | 34 | Co | Mn { South Asia (Hindostan and { | | | { Ceylon) { | | | { 11. NUBIAN | 10 | Co | Mn? { Central Africa (Nubia and { | | | { Fula-land) CURLY-HAIRED { | | | { In all parts of the world, { | | | { having migrated from South +Euplocomi+ { 12. MEDITERRANEAN | 550 | Pr | Pl { Asia to North Africa and { | | | { South Europe (about 600 millions) { | | | { | | | | | | { In all parts of the world, 13. HYBRIDS | 11 | Pr | Pl { but predominating in America OF THE | | | { and Asia SPECIES | | | --------------------+--------+ | TOTAL 1350

CHAPTER XXIV.

OBJECTIONS AGAINST, AND PROOFS OF THE TRUTH OF, THE THEORY OF DESCENT.

Objections to the Doctrine of Filiation.-Objections of Faith and Reason.-Immeasurable Length of the Geological Periods.-Transition Forms between Kindred Species.-Dependence of Stability of Form on Inheritance, and of the Variability of Form on Adaptation.-Origin of very complicated Arrangement of Organisation.-Gradual Development of Instincts and Mental Activities.-Origin of a priori Knowledge from Knowledge a posteriori.-The Knowledge requisite for the Correct Understanding of the Doctrine of Filiation.-Necessary Interaction between Empiricism and Philosophy.-Proofs of the Theory of Descent.-Inner Causal Connection between all the Biological Series of Phenomena.-The Direct Proof of the Theory of Selection.-Relation of the Theory of Descent to Anthropology.-Proofs of the Animal Origin of Man.-The Pithecoid Theory as an Inseparable Part of the Theory of Descent.-Induction and Deduction.-Gradual Development of the Human Mind.-Body and Mind.-Human Soul and Animal Soul.-A Glance at the Future.

If in these chapters I may hope to have made the Theory of Descent seem more or less probable, and to have even convinced some of my readers of its una.s.sailable truth, yet I am by no means unconscious that, to most of them, during the perusal of my explanations, a number of objections more or less well founded must have occurred. Hence it seems absolutely necessary at the conclusion of our examination to refute at least the most important of these, and at the same time, on the other hand, once more to set forth the convincing arguments which bear testimony to the truth of the theory of development.

The objections which are raised to the doctrine of descent may be divided into two large groups: objections of faith and objections of reason. The objections of the first group originate in the infinitely varied forms of faith held by human individuals, and need not here be taken into consideration at all. For, as I have already remarked at the beginning of this book, science, as an objective result of sensuous experience, and of the striving of human reason after knowledge, has nothing whatever to do with the subjective ideas of faith, which are preached by a single man as the direct inspirations or revelations of the Creator, and then believed in by the dependent mult.i.tude. This belief, very different in different nations, only begins, as is well known, where science ends. Natural Science believes, according to the maxim of Frederick the Great, "that every one may go to heaven in his own fashion," and only necessarily enters into conflict with particular forms of faith where they appear to set a limit to free inquiry and a goal to human knowledge, beyond which we are not to venture. Now this is certainly the case here in the highest degree, for the Theory of Development applies itself to the solution of the greatest of scientific problems-that of the creation, the coming into existence of things; more especially the origin of organic forms, and of man at their head. It is here certainly the right as well as the sacred duty of free inquiry, to fear no human authority, and courageously to raise the veil from the image of the Creator, unconcerned as to what natural truth may lie concealed beneath. The only Divine revelation which we recognise as true, is written everywhere in nature, and to every one with healthy senses and a healthy reason it is given to partic.i.p.ate in the unerring revelation of this holy temple of nature, by his own inquiry and independent discovery.

If we, therefore, here disregard all objections to the Doctrine of Descent which may be raised by the priests of the different religious faiths, we must nevertheless endeavour to refute the most important of those objections which seem more or less founded on science, and which we grant might, at first sight, to a certain extent captivate us and deter us from adopting the Doctrine of Descent. Many persons seem to think the length of the periods of time required the most important of these objections. We are not accustomed to deal with such immense periods as are necessary for the history of the creation. It has already been mentioned that the periods, during which species originated by gradual trans.m.u.tation, must not be calculated by single centuries, but by hundreds and by millions of centuries. Even the thickness of the stratified crust of the earth, the consideration of the immense s.p.a.ce of time which was requisite for its deposition from water, taken together with the periods of elevation between the periods of depression, indicate a duration of time of the organic history of the earth which the human intellect cannot realize. We are here in much the same position as an astronomer in regard to infinite s.p.a.ce. In the same way as the distances between the different planetary systems are not calculated by miles but by Sirius-distances, each of which comprises millions of miles, so the organic history of the earth must not be calculated by thousands of years, but by palaeontological or geological periods, each of which comprises many thousands of years, and perhaps millions, or even, milliards, of thousands of years. It is of little importance how high the immeasurable length of these periods may be approximately estimated, because we are in fact unable with our limited power of imagination to form a true conception of these periods, and because we do not as in astronomy possess a secure mathematical basis for fixing the approximate length of duration in numbers. But we most positively deny that we see any objection to the theory of development in the extreme length of these periods which are so completely beyond the power of our imagination. It is, on the contrary, as I have already explained in one of the preceding chapters, most advisable, from a strictly philosophical point of view, to conceive these periods of creation to be as long as possible, and we are by so much the less in danger of losing ourselves in improbable hypotheses, the longer we conceive the periods for organic processes of development to have been.

The longer, for example, we conceive the Permian period to have been, the easier it will be for us to understand how the important trans.m.u.tations took place within it which so essentially distinguish the fauna and flora of the Coal period from that of the Trias. The great disinclination which most persons have to a.s.sume such immeasurable periods, arises mainly from the fact of our having in early youth been brought up in the notion that the whole earth is only some thousands of years old. Moreover, human life, which at most attains the length of a century, is an extremely short s.p.a.ce of time, and is not suitable as a standard for the measurement of geological periods. Our life is a single drop in the ocean of eternity. The reader may call to mind the duration of life of many trees which is more than fifty times as long; for example, the dragon-trees (Dracaena) and monkey bread-fruit trees (Adansonia), whose individual life exceeds a period of five thousand years; and, on the other hand, the shortness of the individual life of many of the lower animals, for example, the infusoria, where the individual, as such, lives but a few days, or even but a few hours, contrasts no less strongly with human longevity. This comparison brings the relative nature of all measurement of time very clearly before us.

If the theory of development be true at all, there must certainly have elapsed immense periods, utterly inconceivable to us, during which the gradual historical development of the animal and vegetable kingdom proceeded by the slow transformation of species. There is, however, not a single reason for accepting a definite limit for the length of these periods of development.

A second main objection which many, and more especially systematic zoologists and botanists, raise against the theory of descent, is that no _transition forms_ between the different species can be found, although according to the theory of descent they ought to be found in great numbers. This objection is partly well founded and partly not so, for there does exist an extraordinarily large number of transition forms between living, as well as between extinct species, especially where we have an opportunity of seeing and comparing very numerous individuals of kindred species. Those careful investigators of individual species who so frequently raise this objection are the very persons whom we constantly find checked in their special series of investigations by the really insuperable difficulty of sharply distinguishing individual species. In all systematic works, which are in any degree thorough, one meets with endless complaints, that here and there species cannot be distinguished because of the excessive number of transition forms. Hence every naturalist defines the limit and the number of individual species differently. Some zoologists and botanists, as I mentioned (vol. i. p.

276), a.s.sume in one and the same group of organisms ten species, others twenty, others a hundred or more, while other systematic naturalists again look upon these different forms only as varieties of a single "good" species. In most groups of forms there is, in fact, a superabundance of transition forms and intermediate stages between the individual species.

It is true that in many species the forms of transition are actually wanting, but this is easily explained by the principle of divergence or separation, the importance of which I have already explained. The circ.u.mstance that the struggle for existence is the more active between two kindred forms the closer they stand to each other, must necessarily favour the speedy extinction of the connecting intermediate forms between the two divergent species. If one and the same species produce diverging varieties in different directions, which become new species, the struggle between these new forms and the common primary form will be the keener the less they differ from one another; but the stronger the divergence the less dangerous the struggle. Naturally therefore, it is princ.i.p.ally the connecting intermediate forms which will in most cases quietly die out, while the most divergent forms remain and reproduce themselves as distinct "new species." In accordance with this, we in fact no longer find forms of transition leading to those groups which are becoming extinct, as, for example, among birds, are the ostriches; and among mammals, the elephants, giraffes, Semi-apes, Edentata, and Ornithorhyncus. The groups of forms approaching their extinction no longer produce new varieties, and naturally the species are what is called "good," that is, the species are distinctly different from one another. But in those animal groups where development and progress are still active, where the existing species deviate into many new species by the formation of new varieties, we find an abundance of transition forms which cause the greatest difficulties to systematic naturalists.

This is the case, for example, among birds with the finches; among mammals with most of the rodents (more especially with those of the mouse and rat kind), with a number of the ruminants and with genuine apes, more especially with the South American forms (Cebus), and many others. The continual development of species by the formation of new varieties here produces a ma.s.s of intermediate forms which connect the so-called "good" species, which efface their boundaries, and render their sharp specific distinction completely illusory.

The reason that this nevertheless does not cause a complete confusion of forms, nor a universal chaos in the structure of animals and vegetables, lies simply in the fact that there is a continual counteraction at work between progressive _adaptation_ on the one hand, and the _retentive_ power of _inheritance_ on the other hand. The degree of stability and variability manifested by every organic form is determined solely by the actual condition of the equilibrium between these two opposite functions. _Inheritance is the cause of the stability of species, adaptation the cause of their modification._ When therefore some naturalists say that, according to the theory of descent, there ought to be a much greater variety of forms, and others again, that there ought to be a much greater equality of forms, the former under-estimate the value of inheritance and the latter the value of adaptation. _The ratio of the interaction between inheritance and adaptation determines the ratio of the stability and variability of organic species_ at any given period.

Another objection to the theory of descent, which, in the opinion of many naturalists and philosophers is of great weight, is that it ascribes the origin of organs which act for a definite purpose to causes which are either aimless or mechanical in their operation. This objection seems to be especially important in regard to those organs which appear so excellently adapted for a certain definite purpose that the most ingenious mechanician could not invent a more perfect organ for the purpose. Such are, above all, the higher sense-organs of animals, the eye and ear. If the eyes and auditory apparatus of the higher animals alone were known to us, they would indeed cause great and perhaps insurmountable difficulties. How could we come to the conclusion that the extraordinarily great and wonderful degree of perfection and conformity to purpose which we perceive in the eyes and ears of higher animals, is in every respect attained solely by natural selection?

Fortunately, however, comparative anatomy and the history of development help us here over all obstacles; for when in the animal kingdom we follow the gradual progress towards perfection of the eyes and ears, step by step, we find such a finely graduated series of improvement, that we can clearly follow the development of the most complex organs through all the stages towards perfection. Thus, for example, the eye in the lowest animal is a simple spot of pigment which does not yet reflect any image of external objects, but at most perceives and distinguishes the different rays of light. Later, we find in addition to this a sensitive nerve; then there gradually develops within the spot of pigment the first beginning of the lens, a refractive body which is now able to concentrate the rays of light and to reflect a definite image. But all the composite apparatus for the movement of the eye and its accommodation to variations of light and distance are still absent, namely, the various refractive media, the highly differentiated membrane of the optic nerve, etc., which are so perfectly constructed in higher animals. Comparative anatomy shows us an uninterrupted succession of all possible stages of transition, from the simplest organ to the most highly perfected apparatus, so that we can form a pretty correct idea of the slow and gradual formation of even such an exceedingly complex organ. The like gradual progress which we observe in the development of the organ during the course of individual development, must have taken place in the historical (phyletic) origin of the organ.

Many persons when contemplating these most perfect organs-which apparently were purposely invented and constructed by an ingenious Creator for a definite function, but which in reality have arisen by the aimless action of natural selection-experience difficulties in arriving at a rational understanding of them, which are similar to those experienced by the uncivilized tribes of nature when contemplating the latest complicated productions of engineering. Savages who see a ship of the line, or a locomotive engine for the first time, look upon these objects as the productions of a supernatural being, and cannot understand how a man, an organism like themselves, could have produced such an engine. Even the uneducated cla.s.ses of our own race cannot comprehend such an intricate apparatus in its actual workings, nor can they understand its purely mechanical nature. Most naturalists, however, as Darwin very justly remarks, stand in much the same position in regard to the forms of organisms as do savages to ships of the line and to locomotive engines. A rational understanding of the purely mechanical origin of organic forms can only be acquired by a thorough and general training in Biology, and by a special knowledge of comparative anatomy and the history of development.

Among the remaining objections to the Theory of Descent, I shall here finally refer to and refute but one more, as in the eyes of many unscientific men it seems to possess great weight. How are we, from the Theory of Descent, to conceive of the origin of the mental faculties of animals, and more especially their specific expressions-the so-called instincts? This difficult subject has been so minutely discussed by Darwin in a special chapter of his chief work (the seventh), that I must refer the reader to it. We must regard instincts as essentially the habits of the soul acquired by adaptation, and transmitted and fixed by inheritance through many generations. Instincts are, therefore, like all other habits, which, according to the laws of c.u.mulative adaptation (vol. i. p. 233) and established inheritance (vol. i. p. 216), lead to the origin of new functions, and thus also to new forms of the organs.

Here, as everywhere, the interaction between function and organ goes hand in hand. Just as the mental faculties of man have been acquired by the progressive adaptation of the brain, and been fixed by continual transmission by inheritance, so the instincts of animals, which differ from them only in quant.i.ty, not in quality, have arisen by the gradual perfecting of their mental organ, that is, their central nervous system, by the interaction of Adaptation and Inheritance. Instincts, as is well known, are inherited, but experiences and, consequently, new adaptations of the animal mind, are also transmitted by inheritance; and the training of domestic animals to different mental activities, which wild animals are incapable of accomplishing, rests upon the possibility of mental adaptation. We already know a series of examples, in which such adaptations, after they had been transmitted through a succession of generations, finally appeared as innate instincts, and yet they have only been acquired from the ancestors of the animals. Inheritance has here caused the result of training to become instinct. The characteristic instincts of sporting dogs, shepherd's dogs, and other domestic animals, and the natural instincts of wild animals, which they possess at birth, were in the first place acquired by their ancestors by adaptation. They may in this respect be compared to man's "knowledge a priori," which, like all other knowledge, was originally acquired by our remote ancestors, "a posteriori," by sensuous experience. As I have already remarked, it is evident that "knowledge a priori" arose only by long-enduring transmission, by inheritance of acquired adaptations of the brain, out of originally empiric or experiential "knowledge a posteriori" (vol. i. p. 31).

The objections to the Theory of Descent here discussed and refuted are, I believe, the most important which have been raised against it; I consider also that I have sufficiently proved to the reader their futility. The numerous other objections which besides these have been raised against the Theory of Development in general, or against its biological part, the Theory of Descent in particular, arise either from such a degree of ignorance of empirically established facts, or from such a want of their right understanding, and from such an incapacity to draw the necessary conclusions, that it is really not worth the trouble to go further into the refutation. There are only some general points in regard to which, I should like, in a few words, to draw attention.

In the first place I must observe, that in order thoroughly to understand the doctrine of descent, and to be convinced of its absolute truth, it is indispensable to possess a general knowledge of the whole of the domain of biological phenomena. _The theory of descent is a biological theory_, and hence it may with fairness and justice be demanded that those persons who wish to pa.s.s a valid judgment upon it should possess the requisite degree of biological knowledge. Their possessing a special empiric knowledge of this or that domain of zoology or botany, is not sufficient; they must possess a _general insight into the whole series of phenomena_, at least in the case of one of the three organic kingdoms. They ought to know what universal laws result from the comparative morphology and physiology of organisms, but more especially from comparative anatomy, from the individual and the palaeontological history of development, etc.; and they ought to have some idea of the deep _mechanical, causal connection_ between all these series of phenomena. It is self-evident that a certain degree of general culture, and especially a philosophical education, is requisite; which is, however, unfortunately by many persons in our day, not considered at all necessary. _Without the necessary connection of empirical knowledge and the philosophical understanding of biological phenomena, it is impossible to gain a thorough conviction of the truth of the Theory of Descent._

Now I ask, in the face of this first preliminary condition for a true understanding of the Theory of Descent, what we are to think of the confused ma.s.s of persons who have presumed to pa.s.s a written or oral judgment upon it of an adverse character? Most of them are unscientific persons, who either know nothing of the most important phenomena of Biology, or at least possess no idea of their deeper significance. What should we say of an unscientific person who presumed to express an opinion on the cell-theory, without ever having seen cells; or of one who presumed to question the vertebral-theory, without ever having studied comparative anatomy? And yet one may meet with such ridiculous arrogance any day in the history of the biological Theory of Descent.

One hears thousands of unscientific and but half-educated persons pa.s.s a final judgment upon it, although they know nothing either of botany or of zoology, of comparative anatomy or the theory of tissues, of palaeontology or embryology. Hence it happens, as Huxley well says, that most of the writings published against Darwin are not worth the paper upon which they are written.

We might add that there are many naturalists, and even celebrated zoologists and botanists, among the opponents of the Theory of Descent; but these latter are mostly old stagers, who have grown grey in quite opposite views, and whom we cannot expect, in the evening of their lives, to submit to a reform in their conception of the universe, which has become to them a fixed idea.

It is, moreover, expressly to be remarked, that not only a general insight into the _whole_ domain of biological phenomena, but also a philosophical understanding of it, are the necessary preliminary conditions for becoming convinced of and adopting the Theory of Descent.