REPORT ON THE SEALS. 133 



first to differentiate the angular gyrus (pli courbe) in the brain of Man and Apes, 1 places it 

 behind the supramarginal gyrus, i.e., behind the tier of convolutions immediately above 

 the Sylvian fissure, and therefore in a position corresponding to what that part of the 

 2nd external convolution which gives a similar response to stimulus would assume were 

 this convolution in the Dog's brain pushed backwards by a great development of the 

 frontal lobe. 



The general results arrived at in this comparison of the brains of these Mammals 

 are to some extent to be regarded as tentative and provisional. For, until the 

 development of the fissures and the development and structure of the convolutions have 

 been worked out with greater detail than up to this time has been done, it will not be 

 possible to speak with certainty on all the points which have to be considered in a 

 detailed comparison of the cortex of the cerebrum in the Carnivora with that of Man 

 and Apes. Further, it should be stated that in this, as in other organs of complex 

 constitution, it does not follow that all the parts which are seen in the more highly 

 developed brains are of necessity present, even in a rudimentary condition, in those 

 whose organisation is not so complicated. It must also be remembered that whilst the 

 brains of the Carnivora, and still more so those of the Pinnipedia, are highly convoluted, 

 those of such Apes as the Marmoset Monkey (Ha/pale jacchus) are smooth on the 

 surface, and, with the exception of the large surfaces separated by such fissures as the 

 Sylvian and hippocampal, have no definite subdivision into morphological areas which 

 are capable of being recognised by the naked eye. But both in the Marmoset Monkey 

 and in such other New World Apes as OEdijous, 2 in which the convolutions are either 

 absent or rudimentary, the cerebral hemispheres are prolonged forwards to the front of 

 the olfactory bulbs and backwards above the cerebellum to an extent which is not seen 

 in the Carnivora. In this respect, therefore, these brains, though either without con- 

 volutions or having them only feebly developed, are more highly organised than is the 

 case in the Carnivora proper or in the Seals. 



From the point of view of the hypothesis of evolution there would be no reason to 

 think that the smooth-brained lower Apes had originated out of the Carnivora, at least 

 after the cortex of the cerebrum in this latter order had begun to assume a convoluted 

 arrangement. If they had been derived from a carnivorous animal with a convoluted 

 brain, then in all likelihood the convoluted character of the cerebrum would not have 

 disappeared in the process of evolution. If the higher Apes have been derived by descent 

 from the lower Apes, then the hemispheres in the former with their complex arrangement 

 of fissures and convolutions have been evolved from a smooth-brained stock and not from 

 an animal with such an elaborate arrangement of convolutions as is possessed by either a 

 Dog or a Seal. Hence the acceptance of this hypothesis is not inconsistent with the 



1 Memoire sur les plis CL-rcbraux de l'liomine et des primates, Paris, 1869. 2 See Gratiolet, op. cit. 



