CHAP. IV] THE GENERAL ANATOMY OF THE CERCOPITHECIDAE 139 



iii. The Cercopithecidae maintain the high development of 

 the visual sense noticed previously in the Lemurs and Tarsius. 

 Consequently it is not surprising to find that the form of the 

 cerebrum is strongly influenced by the necessity of providing the 

 requisite mechanism. 



iv. The neopallium is not in all cases very highly convoluted, 

 and consequently the statement regarding the exuberance of its 

 development might seem to be controverted hereby. The rela- 

 tively small size of most of the animals under consideration must 

 evidently be taken into account when this objection is raised. If 

 this be done no appreciable discrepancy of statements remains. 



Some additional details may now be added. The Anthropoidea 

 are microsmatic \ the Cercopithecidae providing no exceptions to 

 this rule. Thus the olfactory bulb is reduced in size, while its 

 tract is pedunculated, i.e. elongated and attenuated in a marked 

 degree. The tuberculum olfactorium is still recognizable, and a 

 remnant of the fissura rhinalis appears as the incisura temporalis 

 (cf. Fig. 84). But the olfactory commissures, i.e. the anterior 

 commissure and the psalterium, together with the fornix, are 

 greatly reduced in relative bulk. The marginal pallium presents 

 no features deserving special comment. 



The large size of the neopallium has been remarked already. 

 The occipital end of the hemisphere overlaps the cerebellum (most 

 extensively in the small American monkeys, Chrysothrix and 

 Hapale). This part of the cortex (the area striata) has peculiar 

 histological features, wherein the Cercopithecidae are approached 

 by Tarsius, while they stand in contrast to the Lemurs. 



The occipital pole of the neopallium contains an extensive 

 posterior cornu of the lateral ventricle of the brain, providing thus 

 the material for comment similar to that just passed on the area 

 striata. 



The plan of the neopallial convolutions is presented in the 

 accompanying illustrations (Figs. 85, 86). The presence of an 

 " insula " in the lower part of the Sylvian fissure demands special 

 notice, as indicative of the local growth of the surrounding parts. 

 The extent of the frontal, parietal, and temporal association areas 

 is shewn in Fig. 85, with which the corresponding diagrams for 

 1 Cf . references to literature on p. 43. 



