NERVOUS SYSTEM. VERTEBRATA. 



occipital element which is found above the calcarine sulcos. 

 Further, on the right hemisphere (in which the notch in 

 the superior margin is absent) the latter element is more 

 strongly marked. 



This apparently hopeless confusion becomes quite intelli- 

 gible if the student remembers (1) that the parieto-occipital 

 sulcus arises merely as a furrow compensatory to the 

 calcarine complex ; (2) that in the interval between the 

 calloso-marginal and calcarine sulci another sulcus (which 

 I have called ' compensatory ") generally makes its appear- 

 ance for reasons similar to those that call the parieto- 

 occipital into being ; and (3) that the relations of the 

 " compensatory ' } sulcus to the calloso-marginal and calcarine 

 sulci are determined mainly by the nature of the other 

 compensatory sulcus, which is the parieto-occipital. 



0. C. 1337 G I. 



D. 574. Two casts of the cranial cavity of a Red Howler (Alo- 

 natta senicula). 



D. 575. The brain o a White-cheeked Capuchin (Cebus lunatus): 

 the left cerebral hemisphere has beeen separated (figs. 235, 

 236, 237, 238). 



Fig. 235. (xf.) 



SULC. CENT. 



...SULC.INTRAPAR. 



SULC. PAR. 



Occupying as it does a central position among the 

 Primates, Cebus lends itself very favourably to a wide 

 comparison. For while its brain has attained to a suffi- 

 ciently high stage of development to permit accurate 



