6io 



THE PRIMATES 



xxm. 4 



squirrels in behaviour. The brain (Fig. 386) has relatively small 

 cerebral hemispheres, not overlapping the cerebellum, but with olfac- 

 tory regions large for a primate, though smaller than in insectivores or 

 other primitive mammals. The nose has numerous well-developed 

 turbinal bones (Fig. 394). The cerebral sulci tend to run longitudinally, 



37 79 18 



Homo 



Cercopithecus 



Fig. 386. Brains of hedgehog and various primates to show the relative development of 

 various parts. The numbers refer to the areas recognized by Brodmann on a basis of their 

 structure. 4 and 6 are the precentral motor areas, 8-12 the frontal and prefrontal areas, 

 lacking in the earliest forms. 1-3 are the end station of skin sensations, and 5 and 7 are also 

 concerned with these. 17 is the visual end station, and 18 and 19 are also concerned with 

 this sense. 22 is the auditory end station, bol, bulbus olfactorius; tol, tuberculum olfac- 



torium. (From Brodmann.) 



rather than transversely as in anthropoids. The whole behaviour is not 

 like that of a monkey; the animals move from branch to branch by 

 sudden leaps, balancing with the long, bushy tail, which is not pre- 

 hensile. Social habits are little developed. 



The snout is long, with a cleft and moist upper lip, the eyes are 

 directed sideways, and the retina contains only rods except in the 

 genus Lemur, which is diurnal and possesses cones. There is no fovea 

 and no binocular vision. The external ears may be large, as in other 

 nocturnal animals. In the skull (Fig. 387) there is a post-orbital bar, 

 but the temporal fossa opens widely to the orbit. The tympanic region 

 shows several peculiar features. The tympanic bone forms a ring, lying 



