THE DESCENT OF THE PRIMATES 23 



anthropoids and man, differing from Simiae 

 Catarhinie, Platyrhina?, and Tarsidie, must have 

 existed tlirougliout tl>e Tertiaries, and must have 

 directly sprung from a Mesozoic insectivorous 

 ancestor, small, in size, but already more or less 

 erect in posture, provided with a spacious brain 

 cavity, with a decidua reflexa, and with a dis- 

 coid placenta of the Erinacean type of develop- 

 ment. Now, in suggesting the existence of this 

 unknown intermediate form, you would not be 

 overdrawing the amount which is booked to the 

 credit of scientific speculation in the bank of 

 probability. As to the smallness in size of 

 Mesozoic Trituberculata, palseontology not only 

 gives ample evidence, but it distinctly does not 

 encourage any other assumption. With regard 

 to a spacious brain cavity, it should be remem- 

 bered that among the South American monkeys 

 certain living genera, by the relative size of 

 their brain, outstrip the Anthropoidea and man 

 himself. Already in 1844 Geoffroy places Chry- 

 sothrix "au premier rang entre tons et a cotd 

 de I'homme m^me, si ce n'est au-dessus, par la 

 masse proportionnelle de leur cerveau," at the 

 same time drawing attention to the fact that 

 the brain convolutions are very much less de- 

 veloped, these convolutions being to a great 



