Vnw. VIT. Strttcture of the Brain. 205 



Tiew that mnn lins bepn evolved from some npe-like firm ; though there 

 ean be uo donbt that tliat foim was, in many respects, diffeient from 

 any member of the Primates now livitg. 



Von Buer taught ua, half a century ago, that, in the oonrse of theii 

 development, allied animals put on, at first, the characters nf the greater 

 groups to wliicdi they belong, and, by degrees, assume those wliioli restrict 

 them within the limits of their family, genus, and species ; and he 

 proved, at the same time, that no developmental stage of a highel 

 iinimal is precisely similar to the adult condition of any lower animal. 

 It is quite correct to say that a frog passes through the condition of a 

 fish, Uiaamuch as at one period of its life the tadpole has all the cha- 

 racters of a fish, and, if it went no further, would have to be grouped 

 among fishes. But it is equally true that a tadpole io very different 

 from any known fish. 



In like manner, the bruin of a human fcetus, at the fifth month, may 

 correctly be said to be, not only the brain of an ape, but that of a 1 

 Arot.ipirhecine or marmoset-like ape; for its htmispheres, with their 

 great posterior lobster, and with no sulci but the sylvian and the 

 calcurine, present the characteristics found only in the group of the 

 Arctopilhecine Primates. But it is eqnally true, as Gratiolet remarks, 

 that, in its widely open sylvian fissure, it difters from the biain of any 

 actual marmoset. No doubt it would be much more similar to the brain 

 of an advanced foetus of a marmoset. But we know nothing whatever 

 of the development of the brain in the marmosets. In the Platyrhini 

 pi-oper, the only observation with which I am acquainted is due to 

 Pansch, who found in the brain of a fcetal Cebus Apella, in addition to 

 the sylvian fissure and the deep oalcarine fissure, only a very shallow 

 anterotemporal fissure (seissiire paralUle of Gratiolet.) 



Now this fact, taken together with the circumstance that the aiit'TO- 

 temporal sulcus is present in such Platyrhini as the Saimiri, which 

 present mere traces of sulci on the anterior half of the exterior of the 

 cerebral hemispheres, or none at all, undoubtedly, so far as it goes, 

 affiirds fair evidence in favour of Gialiolel's hypothesis, that the 

 posterior sulci appear before the anterior, in the brains of the 

 Platyrhini. But, it by no means follows, that the rule which may hoM 

 good for the Platyrhini extends to the Catarhini. We have no in- 

 formation whatever respecting the development of the brain in the 

 Cyrimnorpha; and, as regards the Anthropomnrpha, nothing but the 

 account of the brain of the Gibbon, near birth, already referred to. 

 At the present niomeni;, there is nut a shadow of evidence to shew 

 that the sulci of a chimpanzee's, or orang's, brain do not appear in the 

 same order as a man's. 



Gratiolet opens his preface with the aphorism. " II est danaereux 

 " dans les sciences de conclure trop vite." I fear he must have for- 

 go. ten this sound maxim by the time he had reached the discussion of 

 the differences between men and apes, in the body of his work. No 

 doubt, the excellent author of one of the most renjarkable contributions 

 to the just understanding of the mammalian brain which has ever been 

 made, would have been the first to admit the insufliciency of his data 

 had he lived to profit by the advance of inquiry. The misfortune ia 

 that his conclusions have been employed by persons incompetent to 

 appreciate their foundation, as arguments in favour of obscurantism." 



«" For example, M. I'Abb^Lecomte winisme et I'origlne de I'Hooroe 

 ID hi; terrible pamphlet 'be Dar- 1873. 



