248 PROF. HUXLEY ON THE [JuuC 1 1, 



of these animals, undertaken with especial reference to the questions 

 under discussion ; and I propose to continue the process of recti- 

 fication thus commenced, by inquiring into another special case — 

 that of Ateles paniscus — and proving, by direct demonstration of the 

 facts, that the three structures, said to be absent even in the highest 

 Apes, are, on the contrary, largely developed* in this comparatively 

 low American monkey, possessed of but a rudiraental thumb upon 

 its hand, and provided with fourniore teeth than the Old World Apes 

 and Man. 



In fact, so far from its being true that the differences between Man 

 and the Apes lie mainly in the cerebral characters, so often referred 

 to, all the evidence now accumulated tends towards the belief that 

 the only three, very striking, cerebral characters, absent in other Mam- 

 malia, which can be truly affirmed to be common to Man and the 

 Old and New World Simice, are exactly these three, — the whole of 

 the true Apes, so far as our present knowledge goes, possessing a 

 posterior lobe, a posterior cornu to the lateral ventricle, and a hip- 

 pocampus minor in that posterior cornu ; while these structures, so 

 far from being in a rudimentary condition, are often more largely 

 developed, in proportion to other parts of the brain, in the Apes than 

 in Man. 



The figures 1 and 2 of Plate XXIX. represent the brains of a male 

 and of a female Ateles of about the same size, as seen from above : 

 both figures were drawn under my own eye by a very competent 

 artist, and are in all essential respects perfectly faithful. It is never- 

 theless obvious that they differ greatly — so much, in fact, that they 

 might readily be supposed to have belonged to different species. 

 The whole difference, however, is due to the circumstance that, while 

 fig. 1 was drawn from an almost fresh brain, fig. 2 represents a brain 

 which had been for several months in spirit f. The roundness of 

 outline of the latter as compared with the former, and the more 

 transverse direction of the fissure of Rolando, are very remarkable ; 

 for the skulls of the two specimens show no particular difference of 

 form. In the unaltered brain, figs. 1, 3, 4, tlie narrowness of the 

 frontal lobes anteriorly, the excavation of their orbital faces, and the 

 flatness of the superior contour are especially worthy of notice. 

 Viewed from above, no part whatsoever of the cerebellum is visible, 

 either at the sides or behind ; while a profile view shows that the 

 cerebral hemispheres projected, for at least ^th of an inch, behind 

 the posterior edge of the cerebellum. Whether this represents the 

 total amount of cerebral overlap or not, I cannot say, in the absence 



* Since this paper was read, Mr. Marshall, F.R.S., has published, in the third 

 number of the ' Natural History Review ' (July 186]) a valuable essay on the 

 Chimpanzee's brain, illustrated by photographs of the parts said to be absent ; and 

 Mr. Flower, in a paper read before the Royal Society (June 20th, 1861), has de- 

 monstrated over agiiin the presence of the same parts in the Orang's brain, has 

 shown their large development in Cebus, and has even proved the presence of a 

 large posterior cornu and of a hippocampus minor in the Lemurine Otolicnus ! 



t The brain of Ateles belzehith, figured by M. Gratiolet, pi. 10. figs. 1, 2, 3, 4, 

 has undergone the same alteiation as that represented in my fig. 2, as might be 

 expected from the fact of its having been long preserved in spirit. 



