the lower grotto of the Le Moustier in Southern France； but this skull has not yet been fully described。 Thus Homo primigenius must also be regarded as occupying a position in the gap existing between the highest apes and the lowest human races； Pithecanthropus； standing in the lower part of it； and Homo primigenius in the higher； near man。 In order to prevent misunderstanding； I should like here to emphasise that in arranging this structural series anthropoid apes； Pithecanthropus； Homo primigenius； Homo sapiensI have no intention of establishing it as a direct genealogical series。 I shall have something to say in regard to the genetic relations of these forms； one to another； when discussing the different theories of descent current at the present day。 （（Since this essay was written Schoetensack has discovered near Heidelberg and briefly described an exceedingly interesting lower jaw from rocks between the Pliocene and Diluvial beds。 This exhibits interesting differences from the forms of lower jaw of Homo primigenius。 （Schoetensack 〃Der Unterkiefer des Homo heidelbergensis〃。 Leipzig； 1908。） G。S。））
In quite a different domain from that of morphological relationship； namely in the physiological study of the blood； results have recently been gained which are of the highest importance to the doctrine of descent。 Uhlenhuth； Nuttall； and others have established the fact that the blood…serum of a rabbit which has previously had human blood injected into it； forms a precipitate with human blood。 This biological reaction was tried with a great variety of mammalian species； and it was found that those far removed from man gave no precipitate under these conditions。 But as in other cases among mammals all nearly related forms yield an almost equally marked precipitate； so the serum of a rabbit treated with human blood and then added to the blood of an anthropoid ape gives ALMOST as marked a precipitate as in human blood； the reaction to the blood of the lower Eastern monkeys is weaker； that to the Western monkeys weaker still； indeed in this last case there is only a slight clouding after a considerable time and no actual precipitate。 The blood of the Lemuridae （Nuttall） gives no reaction or an extremely weak one； that of the other mammals none whatever。 We have in this not only a proof of the literal blood…relationship between man and apes； but the degree of relationship with the different main groups of apes can be determined beyond possibility of mistake。
Finally； it must be briefly mentioned that in regard to remains of human handicraft also； the material at our disposal has greatly increased of late years； that； as a result of this； the opinions of archaeologists have undergone many changes； and that； in particular； their views in regard to the age of the human race have been greatly influenced。 There is a tendency at the present time to refer the origin of man back to Tertiary times。 It is true that no remains of Tertiary man have been found； but flints have been discovered which； according to the opinion of most investigators； bear traces either of use； or of very primitive workmanship。 Since Rutot's time； following Mortillet's example； investigators have called these 〃eoliths；〃 and they have been traced back by Verworn to the Miocene of the Auvergne； and by Rutot even to the upper Oligocene。 Although these eoliths are even nowadays the subject of many different views； the preoccupation with them has kept the problem of the age of the human race continually before us。
Geology； too； has made great progress since the days of Darwin and Lyell； and has endeavoured with satisfactory results to arrange the human remains of the Diluvial period in chronological order （Penck）。 I do not intend to enter upon the question of the primitive home of the human race； since the space at my disposal will not allow of my touching even very briefly upon all the departments of science which are concerned in the problem of the descent of man。 How Darwin would have rejoiced over each of the discoveries here briefly outlined！ What use he would have made of the new and precious material； which would have prevented the discouragement from which he suffered when preparing the second edition of 〃The Descent of Man〃！ But it was not granted to him to see this progress towards filling up the gaps in his edifice of which he was so painfully conscious。
He did； however； have the satisfaction of seeing his ideas steadily gaining ground； notwithstanding much hostility and deep…rooted prejudice。 Even in the years between the appearance of 〃The Origin of Species〃 and of the first edition of the 〃Descent〃； the idea of a natural descent of man； which was only briefly indicated in the work of 1859； had been eagerly welcomed in some quarters。 It has been already pointed out how brilliantly Huxley contributed to the defence and diffusion of Darwin's doctrines； and how in 〃Man's Place in Nature〃 he has given us a classic work as a foundation for the doctrine of the descent of man。 As Huxley was Darwin's champion in England； so in Germany Carl Vogt； in particular； made himself master of the Darwinian ideas。 But above all it was Haeckel who； in energy； eagerness for battle； and knowledge may be placed side by side with Huxley； who took over the leadership in the controversy over the new conception of the universe。 As far back as 1866； in his 〃Generelle Morphologie〃； he had inquired minutely into the question of the descent of man； and not content with urging merely the general theory of descent from lower animal forms； he drew up for the first time genealogical trees showing the close relationships of the different animal groups； the last of these illustrated the relationships of Mammals； and among them of all groups of the Primates； including man。 It was Haeckel's genealogical trees that formed the basis of the special discussion of the relationships of man； in the sixth chapter of Darwin's 〃Descent of Man〃。
In the last section of this essay I shall return to Haeckel's conception of the special descent of man； the main features of which he still upholds； and rightly so。 Haeckel has contributed more than any one else to the spread of the Darwinian doctrine。
I can only allow myself a few words as to the spread of the theory of the natural descent of man in other countries。 The Parisian anthropological school； founded and guided by the genius of Broca； took up the idea of the descent of man； and made many notable contributions to it （Broca； Manouvrier； Mahoudeau； Deniker and others）。 In England itself Darwin's work did not die。 Huxley took care of that； for he； with his lofty and unprejudiced mind； dominated and inspired English biology until his death on June 29； 1895。 He had the satisfaction shortly before his death of learning of Dubois' discovery； which he illustrated by a humorous sketch。 （〃Life and Letters of Thomas Henry Huxley〃； Vol。 II。 page 394。） But there are still many followers in Darwin's footsteps in England。 Keane has worked at the special genealogical tree of the Primates； Keith has inquired which of the anthropoid apes has the greatest number of characters in common with man； Morris concerns himself with the evolution of man in general； especially with his acquisition of the erect position。 The recent discoveries of Pithecanthropus and Homo primigenius are being vigorously discussed； but the present writer is not in a position to form an opinion of the extent to which the idea of descent has penetrated throughout England generally。
In Italy independent work in the domain of the descent of man is being produced； especially by Morselli； with him are associated； in the investigation of related problems； Sergi and Giuffrida…Ruggeri。 From the ranks of American investigators we may single out in particular the eminent geologist Cope； who championed with much decision the idea of the specific difference of Homo neandertalensis （primigenius） and maintained a more direct descent of man from the fossil Lemuridae。 In South America too； in Argentina； new life is stirring in this department of science。 Ameghino in Buenos Ayres has awakened the fossil primates of the Pampas formation to new life； he even believes that in Tetraprothomo； represented by a femur； he has discovered a direct ancestor of man。 Lehmann…Nitsche is working at the other side of the gulf between apes and men； and he describes a remarkable first cervical vertebra （atlas） from Monte Hermoso as belonging to a form which may bear the same relation to Homo sapiens in South America as Homo primigenius does in the Old World。 After a minute investigation he establishes a human species Homo neogaeus； while Ameghino ascribes this atlas vertebra to his Tetraprothomo。
Thus throughout the whole scientific world there is arising a new life； an eager endeavour to get nearer to Huxley's problema maximum； to penetrate more deeply into the origin of the human race。 There are to…day very few experts in anatomy and zoology who deny the animal descent of man in general。 Religious considerations； old prejudices； the reluctance to accept man； who so far surpasses mentally all other creatures； as descended from 〃soulless〃 animals； prevent a few investigators from giving full adherence to the doctrine。 But there are very few of these who still postulate a special act of creation for man。 Although the majority of experts in anatomy and zoology accept unconditionally the descent of man from lower forms； there is much diversity of opinion among them in regard to the special line of descent。
In trying to establish any special hypothesis of descent； whether by the graphic method of drawing up genealogical trees or otherwise； let us always bear in mind Darwin's words （〃Descent of Man〃； page 229。） and use them as a critical guiding line： 〃As we have no record of the lines of descent； the pedigree can be discovered only by observing the degrees of resemblance between the beings which are to be classed。〃 Darwin carries this further by stating 〃that resemblances in several unimportant structures； in useless and rudimentary organs； or not now functionally active； or in an embryological condition； are by far the most serviceable for classification。〃 （Loc。 cit。） It has also to be