AND AFFINITIES OF TARSIUS. 



483 



long before there is any trace of a connecting stalk, from which 

 we may conclude that it does not arise like that of Tao'sius. It 

 is possible that it takes origin as a diffuse proliferation from the 

 marginal ectoderm of the amnio-embryona] vesicle, as is said to 

 be the case in Gcdeo'pithecus and 7\ttusia, a mode of origin which 

 assuredly is purely secondary and adaptive. 



In respect, then, of these developmental occurrences, it is 

 evident, I think, that Tarsias provides the intermediate link 

 between the primitive Lemuroids and the highly specialised 

 Anthropoids. 



We may pass on now to the consideration of the two features 

 in the development of Tarsius to which Hubrecht attached most 



Text-fiaure 4. 



Rmn. el 



/Qmn. 



Tarsius spectrum. Diagram (after Hubreclit) to show the relations of the foetal 

 membranes after closure of the amnion (amn.). Note the temporary con- 

 nection between the amnion and the chorion, marking the last point of closure 

 (amn.cl.). Other reference-letters as in text-fig. 3. 



importance as guides to its affinity, viz., the occurrence of a 

 connecting or ventral stalk and the presence of a massive 

 placenta of the hfemochorial deciduate tj^'pe. When Hubrecht 

 first put forward his views, the existence of a connecting stalk 

 outside Tarsius and the Anthropoids was unknown, and so he 

 naturally attaclied great importance to it as a token of affinity, 

 but we now know, through the researches of Newman and 

 Proc. Zool. See— 1919, No. XXXIII. 33 



