INTRODUCTION TO PART II 



VALID objections may be urged against the establishment of such a 

 group as the inlcrmcdiuU' ])rimatts upon phylogenetic or paleonto- 

 logical grounds. But there arc substantial reasons for this distinction 

 because of certain likenesses in these brains. It should be understood, however, 

 that such similarities as do exist in the enccphalon of this intermediate group 

 do not constitute an entirely satisfactory basis for the far-reaching generic 

 associations which this grouping would seem to imply. They offer convenient 

 criteria for distinguishing between those forms possessed of brains having 

 relatively the most simple design, and those which have become more complex 

 in their constitution. 



The intermediate primates comprise all of the old-world monkeys with 

 the exception of the three great man-like apes. According to this classifica- 

 tion, the Hylobatidae or gibbons fall into the intermediate class. This group 

 also comprises all of the members of the great family of Lasiopygidae, which 

 includes the baboons, mandrils, the macaques and cynocephalous monkeys, 

 the mangabeys, gucnons and langeurs. The most forcible objection which 

 might be urged against the inclusion of the gibbons in this group is their 

 many striking anthropoid characters. A survey of the central nervous system 

 of these primates, however, would seem to justify the view that they are in 

 many respects more primitive than the man-like apes. In size of brain and 

 in configuration of fissural pattern, the gibbons come much nearer to the 

 lasiopygidal species than they do to the higher anthropoids. 



The species of intermediate primates selected for description include 

 Papio cynocephalus (Cynocephalus babuin), one of the large dog-headed 

 baboons, Pithecus rhesus (Macacus rhesus), the common macaque of India, 



and Hylobates hoolock, the gibbon. 



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