494 THE PHYSIOLOGY OF REPRODUCTION 



blastocyst and the small anmiotic and hypoblastic vesicles. In the 

 ovum described by Leopold, 1 it was' already split by the " Haftstiel " 

 into two parts, which enclosed the coelom and were continuous with 

 each other (Fig. 149). The outer wall of the blastocyst, the fo-tal 

 ectoderm or trophoblast which anchors the ovum in the mucosa, is 



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thickened all round its circumference, and even in the earliest 

 specimen contained vacuoles into some of which maternal blood had 

 penetrated. In this thick spongy layer Bryce and Teacher found no 

 cell-outlines anywhere. Hence the transformation to syneytium is not 

 due, as Peters supposed, to the contact with maternal blood. Under 

 the syncytiurn is the cellular layer, corresponding to the cytoblast of 



1 Leopold, " Demonstration eines sehr jungen menschlichen Eies," .\r\K-iti-n 

 d. Konigl. F/-> "'/./;, ,/'/. in />/vW/-//, Leipzig, 1906. 



