468 THE PHYSIOLOGY OF REPRODUCTION 



youngest ovum the formation of these buds was just commencing, 

 and, according to Bryce and Teacher, they tended to grow out 

 not so much into the strands of trophoblast as into the spaces 



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between them. Later still, mesoblastic processes penetrate into 

 the cellular buds and complete the vascular chorionic villi. 



Round the blastodermic vesicle is a zone of degenerated tissue, 

 the " Detrituszone " (Fig. 124). It is uncertain whether it is 

 formed by the influence of the trophoblast or maternal elements. 



