AND AFFINITIES OF TARSIUS. 469 



Bi'odmann not only examined (in Yogt's laboratory) the 

 microscopic structure of the Lemur's cortex, but also made an 

 elaborate comparison between it and the cortex of the Apes and 

 a considerable series of othei' mammals *. He arrived at the 

 conclusion that in the arrangement of its cells and fibres the 

 Lemur's cortex reveals " weitgehende Uebereinstiiximung mit 

 den Primaten [i. e. Simise], in einzelnen jedocli Abweichungen 

 niancher cytoarchitektonischer Typen teils im Siune einer 

 niederen, teils aber audi im Sinne einer hoheren Differenzierung 

 aufweist." 



Brodmann did not examine the brain of Tarsius ; but my own 

 studies enable me to say that its visual cortex is not only more 

 extensive than that of the Lemuroidea, but also more highly 

 differentiated and more like that of the Apes. The other regions 

 of the cortex, however, conform much moi'e closely to the 

 corresponding areas in the Lemuroidea, both in extent and in 

 structure, than to those of the Apes. 



The Tarsioidea seem to have become differentiated from the 

 Lemuroidea by a reduction of the face, which permitted the much 

 fuller development of stereoscopic vision. This in turn stimulated 

 the higher specialisation of the visual cortex and provided the 

 guidance for the performance of movements of a much greater 

 skill and precision. It was the cultivation of these powers that 

 brought one branch of the Tarsioidea to Simian rank. 



Not content with the recognition of the fact that the Apes 

 were derived from the Suborder Tarsioidea, some of those who 

 are taking part in this discussion want to promote Tarsius to the 

 full status of an Ape. This is an unwarrantable claim. The 

 anatomy of every part of the body, and more jjarticularly of the 

 brain, reveals the extent of the profound difference between 

 the Anthropoidea and the Tarsioidea. On the present occasion I 

 shall not attempt to enumerate all the criteria of a true Ape, and 

 shall I'efer only to one point (which, however, is of fimdamental 

 importance as a distinctive feature between the Anthropoidea 

 and the other two Suborders of the Primates). In the true ApeS 

 all the great cortical areas to which I have already referred 

 (visual, auditory, tactile, and motor) are very much larger and 

 more highly differentiated than they are either in the Tarsioidea 

 or tlie Lemuroidea. But, in addition, the relatively insignificant 

 parietal, temporal, and frontal '■ association areas " of the Pi'O- 

 simia? have undergone so much expansion that the brain of a real 

 monkey is, at least, about three or four times the bulk of that of 

 a Tarsioid or Lemuroid of the same size ; and these overgrown 

 territories have also become highly differentiated and specialised. 

 In my Linnean memoir (1902), to which I have already referred, 

 the data for comparing the size of the brain in different mammalian 

 Orders has been set foi'th, so that I need refer here only to one 

 relevant point. 



* ' Vei'gleicli. Lokalisatioiislehre der Grosshirnrinde/ 1909. 



32* 



