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onvinced of the influence of external conditions。 In 1876； that is； two years after the appearance of the second edition of 〃The Descent of Man〃； he writes with his usual candid honesty： 〃In my opinion the greatest error which I have committed； has been not allowing sufficient weight to the direct action of the environment； i。e。 food； climate； etc。 independently of natural selection。〃 （Ibid。 Vol。 III。 page 159。） It is certain from this change of opinion that； if he had been able to make up his mind to issue a third edition of 〃The Descent of Man〃； he would have ascribed a much greater influence to the effect of external conditions in explaining the different characters of the races of man than he did in the second edition。 He would also undoubtedly have attributed less influence to sexual selection as a factor in the origin of the different bodily characteristics； if indeed he would not have excluded it altogether。
In Part III of the 〃Descent〃 two additional chapters are devoted to the discussion of sexual selection in relation to man。 These may be very briefly referred to。 Darwin here seeks to show that sexual selection has been operative on man and his primitive progenitor。 Space fails me to follow out his interesting arguments。 I can only mention that he is inclined to trace back hairlessness； the development of the beard in man； and the characteristic colour of the different human races to sexual selection。 Since bareness of the skin could be no advantage； but rather a disadvantage； this character cannot have been brought about by natural selection。 Darwin also rejected a direct influence of climate as a cause of the origin of the skin…colour。 I have already expressed the opinion； based on the development of his views as shown in his letters； that in a third edition Darwin would probably have laid more stress on the influence of external environment。 He himself feels that there are gaps in his proofs here； and says in self…criticism： 〃The views here advanced； on the part which sexual selection has played in the history of man； want scientific precision。〃 （〃Descent of Man〃； page 924。） I need here only point out that it is impossible to explain the graduated stages of skin… colour by sexual selection； since it would have produced races sharply defined by their colour and not united to other races by transition stages； and this； it is well known； is not the case。 Moreover； the fact established by me （〃Die Hautfarbe des Menschen〃； 〃Mitteilungen der Anthropologischen Gesellschaft in Wien〃； Vol。 XXXIV。 pages 331…352。）； that in all races the ventral side of the trunk is paler than the dorsal side； and the inner surface of the extremities paler than the outer side； cannot be explained by sexual selection in the Darwinian sense。
With this I conclude my brief survey of the rich contents of Darwin's book。 I may be permitted to conclude by quoting the magnificent final words of 〃The Descent of Man〃： 〃We must； however； acknowledge； as it seems to me； that man； with all his noble qualities； with sympathy which feels for the most debased； with benevolence which extends not only to other men but to the humblest living creature； with his god…like intellect which has penetrated into the movements and constitution of the solar systemwith all these exalted powersMan still bears in his bodily frame the indelible stamp of his lowly origin。〃 （Ibid。 page 947。）
What has been the fate of Darwin's doctrines since his great achievement？ How have they been received and followed up by the scientific and lay world？ And what do the successors of the mighty hero and genius think now in regard to the origin of the human race？
At the present time we are incomparably more favourably placed than Darwin was for answering this question of all questions。 We have at our command an incomparably greater wealth of material than he had at his disposal。 And we are more fortunate than he in this respect； that we now know transition…forms which help to fill up the gap； still great； between the lowest human races and the highest apes。 Let us consider for a little the more essential additions to our knowledge since the publication of 〃The Descent of Man〃。
Since that time our knowledge of animal embryos has increased enormously。 While Darwin was obliged to content himself with comparing a human embryo with that of a dog； there are now available the youngest embryos of monkeys of all possible groups （Orang； Gibbon； Semnopithecus； Macacus）； thanks to Selenka's most successful tour in the East Indies in search of such material。 We can now compare corresponding stages of the lower monkeys and of the Anthropoid apes with human embryos； and convince ourselves of their great resemblance to one another； thus strengthening enormously the armour prepared by Darwin in defence of his view on man's nearest relatives。 It may be said that Selenka's material fils up the blanks in Darwin's array of proofs in the most satisfactory manner。
The deepening of our knowledge of comparative anatomy also gives us much surer foundations than those on which Darwin was obliged to build。 Just of late there have been many workers in the domain of the anatomy of apes and lemurs； and their investigations extend to the most different organs。 Our knowledge of fossil apes and lemurs has also become much wider and more exact since Darwin's time： the fossil lemurs have been especially worked up by Cope； Forsyth Major； Ameghino； and others。 Darwin knew very little about fossil monkeys。 He mentions two or three anthropoid apes as occurring in the Miocene of Europe （〃Descent of Man〃； page 240。）； but only names Dryopithecus； the largest form from the Miocene of France。 It was erroneously supposed that this form was related to Hylobates。 We now know not only a form that actually stands near to the gibbon （Pliopithecus）； and remains of other anthropoids （Pliohylobates and the fossil chimpanzee； Palaeopithecus）； but also several lower catarrhine monkeys； of which Mesopithecus； a form nearly related to the modern Sacred Monkeys （a species of Semnopithecus） and found in strata of the Miocene period in Greece； is the most important。 Quite recently； too； Ameghino's investigations have made us acquainted with fossil monkeys from South America （Anthropops； Homunculus）； which； according to their discoverer； are to be regarded as in the line of human descent。
What Darwin missed most of allintermediate forms between apes and man has been recently furnished。 （E。 Dubois； as is well known； discovered in 1893； near Trinil in Java； in the alluvial deposits of the river Bengawan； an important form represented by a skull…cap； some molars； and a femur。 His opinionmuch disputed as it has beenthat in this form； which he named Pithecanthropus； he has found a long…desired transition…form is shared by the present writer。 And although the geological age of these fossils； which； according to Dubois； belong to the uppermost Tertiary series； the Pliocene； has recently been fixed at a later date （the older Diluvium）； the MORPHOLOGICAL VALUE of these interesting remains； that is； the intermediate position of Pithecanthropus； still holds good。 Volz says with justice （〃Das geologische Alter der Pithecanthropus…Schichten bei Trinil； Ost…Java〃。 〃Neues Jahrb。 f。Mineralogie〃。 Festband； 1907。）； that even if Pithecanthropus is not THE missing link； it is undoubtedly _A_ missing link。
As on the one hand there has been found in Pithecanthropus a form which； though intermediate between apes and man； is nevertheless more closely allied to the apes； so on the other hand； much progress has been made since Darwin's day in the discovery and description of the older human remains。 Since the famous roof of a skull and the bones of the extremities belonging to it were found in 1856 in the Neandertal near Dusseldorf； the most varied judgments have been expressed in regard to the significance of the remains and of the skull in particular。 In Darwin's 〃Descent of Man〃 there is only a passing allusion to them （〃Descent of Man〃； page 82。） in connection with the discussion of the skull…capacity； although the investigations of Schaaffhausen； King； and Huxley were then known。 I believe I have shown； in a series of papers； that the skull in question belongs to a form different from any of the races of man now living； and； with King and Cope； I regard it as at least a different species from living man； and have therefore designated it Homo primigenius。 The form unquestionably belongs to the older Diluvium； and in the later Diluvium human forms already appear； which agree in all essential points with existing human races。
As far back as 1886 the value of the Neandertal skull was greatly enhanced by Fraipont's discovery of two skulls and skeletons from Spy in Belgium。 These are excellently described by their discoverer （〃La race humaine de Neanderthal ou de Canstatt en Belgique〃。 〃Arch。 de Biologie〃； VII。 1887。）； and are regarded as belonging to the same group of forms as the Neandertal remains。 In 1899 and the following years came the discovery by Gorjanovic… Kramberger of different skeletal parts of at least ten individuals in a cave near Krapina in Croatia。 （Gorjanovic…Kramberger 〃Der diluviale Mensch von Krapin