ON THE FOETAL MEMBRANES OF OHELONIA. 53 



peeled the hypoblast off the proamnion, and the head 

 is now enclosed in the amniotic cap consisting of the 

 epiblast and mesohlast. Although these diagrams (III, 

 IV and V) show the encroachment of the mesoblast on 

 the proamnion as taking place from before backward, 

 it in reality takes place mostly from two sides. In 

 Diags. IV and V, the gradual development of the 

 allantois is shown. 



Diag. VI. Shows the fœtal membranes of Clemmys as com- 

 pleted. 



Diag. VII. Shows the foetal membranes of Trionyx as com- 

 pleted. 



