122 ANIMAL LIFE AND HUMAN PROGRESS 



developed structure .is not necessarily the most highly special- 

 ised structure, for it is possible that the best may be produced 

 by generalised development. Most will, I think, agree that 

 therein lies the perfection of the human brain it is a perfect 

 example of generalised development of the Eutherian mam- 

 malian brain. It shows what may be called an all-round 

 development. The brains of the anthropoid apes (and, with 

 regard to perhaps the greatest number of isolated points, that 

 of the gorilla) approach at times to a close approximation to this 

 condition of human general development. But for the most 

 part (and especially in the chimpanzee) they are committed to 

 some side line of specialisation, which becomes more pro- 

 nounced as the phylum of the Old World monkeys is passed 

 in review. To take only one region of the brain, the chim- 

 panzee appears to be definitely committed to that line of 

 simian specialisation which finds one expression in the develop- 

 ment of the so-called " simian sulcus." and I agree with those 

 who see marked affinities to the baboons and macaques in 

 the brain of the chimpanzee. The other anthropoids share 

 definitely in this tendency, the gorilla inclining towards the 

 lower African monkeys, the orang maybe more towards the 

 Asiatic Semnopithecidae, but all towards the Old World 

 monkey specialisation, not towards a primitive mammalian 

 generalisation. The New World monkeys, on the other hand, 

 appear to be not so definitely committed to those specialisa- 

 tions which are so characteristic of the Old World monkeys ; 

 and in the Woolly Monkeys (Lagothrix) there is evinced a 

 tendency to generalised development which is strikingly 

 reminiscent of human characters. So far there is but little 

 recorded observation upon this subject, but nevertheless one 

 may more aptly compare the mentality of the American 

 monkeys with human cerebral processes, than we can grade 

 over that very wide gulf which separates the mentality of the 

 macaques and baboons from anything which is characteristic- 

 ally " human " in the best connotation of this word. 



Even with such a slender outline as this it will be seen 

 that there is some difficulty in imagining that human cerebral 

 characteristics have been attained along the route of the 



