438 



human brains that I have studied it is possible to recognise every 

 transitional stage in the disintegration of such characteristically pithe- 

 coid types as are represented in Figures 1 and 3 and to identify in 

 the maze of irregular sulci of most human brains the undoubted 

 homologues of the occipital sulci of the Apes. 



In this note I wish especially to call attention to a means not 

 only of checking the evidence of mere surface -anatomy but also of 

 absolutely demonstrating the homology of the sulcus lunatus of the 

 human brain with the "Affenspalte", This new criterion is afforded 

 by the study of the distribution of the stria Gennari in the occipital 

 cortex. This white line is so sharply defined in part of the occipital 

 cortex in Man and the Apes that the stria-bearing region — or "area 



occ. trans. 



inc. par, occ. 



s. intrapar. 



s. lunat 



s. lunat. 



s. ace. i. 1. 



s. 1. m. 



s. iufrastr. 



Fig. 3. The caudal aspects of the right cerebral hemisphere of a young Chim- 

 panzee (Anthropopithecus troglodytes Schweinfurthi from tlie Niam-Niam Country) and 

 the left cerebral hcmisi)herc of an adult male Egyptian. 



striata", as we may call it — can be mapped out in sections of the 

 fresh brain with absolute exactness. The stria Gennari stops so ab- 

 ruptly on all sides that its edges are plainly visible to the naked eye : 

 it thus affords us a simple and sure means of identifying a definite 

 area, which there is every reason for regarding as homologous in the 

 brains of the various Primates. 



