FCETAL NUTRITION: THE PLACENTA 457 



epithelium 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 villi. In the syncytium the circulating maternal 



,.' 







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 ; 

 c 2/-> cytoblast ; g.s. , gland secretion. 



blood provides for the exchange of gases, and supplements the 

 nutriment supplied by the glandular secretion. 



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

 fied by the characteristics of the uterine mucosa. Hubrecht x 



1 Hubrecht, " Ueber die Entwicklung der Placenta von Tarslus und 

 Tupaja" Internat. Congr. of ZooL, Cambridge, 1898. 



