494 THE PHYSIOLOGY OF REPRODUCTION 



blastocyst and the small amniotic and hypoblastie vesicles. In the 

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

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

 each other (Fig. 149). The outer wall of the blastocyst, the foetal 

 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 syncytium is not 

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

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



1 Leopold, " Demonstration eines sehr jungen menschlichen Eies," Arbeitcn 

 aus d. Kmiigl. FrauenMinik in Dresden, Leipzig, 1906. 



