F(ETAL NUTRITION: THE PLACENTA 457 



epitheKum at the point of connection with the blastocyst, the 

 plasmodiblast penetrates into the connective tissue layer which 

 forms a symplasma. It is followed by the cytoblast and the 

 allantoic vilh. In the syncytium the circulating maternal 







ff^- 



cy- 



pL- 



771- 



-ae 



Jw -v— ' ■■■ ■■ 



(? //,, « « '^ 



Fig. 117. — Orifice of a uterine gland of the mole with trophoblastic dome. 



(From Vernhout's "Ueber die Placenta des Maulwurfs," Anat. Hefte, 



vol. v., 1894.) 

 m., uterine mucous membrane ; ue., uterine epithelium; pi., plasmodiblast ; 

 cy. , cytoblast ; g.s., gland secretion. 



blood provides for the exchange of gases, and supplements the 

 nutriment supphed by the glandular secretion. 



Tupaia. — In Tupaia javanica also, the placentation is modi- 

 fied by the characteristics of the uterine mucosa. Hubrecht ^ 



' Hubrecht, " Ueber die Entwicklung der Placenta von Tarsius und 

 Tv/paja," Intemat. Congr. of Zool., Cambridge, 1898. 



