C XXIX 



THE SIGNIFICANCE OF THE STRLCTL R-\L HOMOGENEITY' AND 



SPECIFIC MODIFICATIONS IN THE PRLMATE BR.AIN. 



THEIR RELATION TO THE PROGRESSIX E 



ADAPTATION OF BEHAMOR 



The Primate Bbain as Evie : Closely Int^ d 



Primate Order 



r 



1 



^ : . ^ they are in e.\: „_.ce, stand out in 



- jle definition as a closely integrated order in consequence 



-*" "■" '-a5t one constant mark of identifrcstion, the brain. If in other 



It-: 



struc " - ::e ordinal association of t ates might be doubted, 



this I " of their organizat!*^r! wrviild set .bts aside. Even in the 



exter .of the b" iite«. there are featiires which 



them tosrether by ^ _ _'\"astG .teat 



- e hesitancy in recognizing the essential similarir'.- that 



exists between t These similarities constitute a fr>rm: - ogue 



of homologous features. Some nine or ten of th*^ ntioned and 



discussed. 



ESSENTIAL ORDINAL SIMILARITIES OF \IN 



The Encephalic Indices. The encep . .dices of these brains, 

 almost without : •=pec!f!cation, set the primates apart in an order by 



themselves. .-MI of thest^ < possess a forebrain ir\6ex above 80 per cent, 



both by weight e brain. The . anying table shows 



how this index ..ptive process c. .ts especially to the 



predominant -ce of the differentiation of the forelimb. Those animals 

 whose i>ectL. ages are sp>ecialized as wings, fins or |>addles do not 



