THE HOWLERS. 1 91 



size, and complexity of convolutions are observed in the 

 Chimpanzee and Gorilla, leading up to the brain of Man. 

 Among the New World genera there is a much greater diver- 

 gence. Among the Capuchins (Cebus), and among them only, 

 there is a precise repetition of the Old World type ; but in 

 the genus Mycetes we have modifications in which there is no 

 parallel among the Catarrhine (or Old World) series. There is 

 an absence in its brain of signs of serial elevation ; and it 

 exhibits a great dissimilarity to all, even the lowest of the Old 

 World forms, and to those American Monkeys, which in brain- 

 character closely resemble Old World Apes. It shows an 

 affinity in some of its more striking characters to such low 

 forms of New World Apes as Nyctipithecus, The low type of 

 brain is in keeping, as Sir William Flower further observes, 

 with their surly and untameable disposition, and with the 

 observation that their intelligence is of a very different order 

 from that of their neighbours, the Spider-Monkeys and 

 Capuchins of higher cerebral organisation. 



" When Howlers are seen in the forest," remarks Mr. Bates, 

 " there are generally three or four of them mounted on the 

 topmost branches of a tree. It does not appear that their 

 harrowing roar is emitted from sudden alarm ; at least, it was 

 not so in captive individuals. It is probable, however, that 

 the noise serves to intimidate their enemies." The muscular 

 power employed in giving vent to their cavernous roar appears 

 to be small. Their food consists chiefly of fruits and leaves. 



In colour the Howlers vary very much. The young of both 

 sexes often differ from their parents, and the females from the 

 males, and there is also great individual variation. 



The geographical distribution of some of the species is very 

 restricted, several of them being confined to a special district 



