118 



EDWARD MCCRADY, JR. 



The description thus far has been written with primary 

 reference to the chorion, but it has necessarily included a sort 

 of implicit description of the amnion. It has already been 



s.ch. 



nvick 



nv.ch. 



G.ch. 



nv.ch. 



B 



nv,ch 



D 



Fig. 40 Diagrammatic sections of vesicles to show the relations of extra- 

 embryonic membranes in the opossum and the rabbit. The heavy line represents 

 ectoderm; the light line mesoderm; the dotted line endoderm. A, opossum 

 stage 29. B, opossum stage 33. C, rabbit at 10 days. D, rabbit at 13 days. 



indicated, for instance, that the head fold is composed entirely 

 of proamnion, and that the tail fold and lateral folds are 

 formed of the somatopleuric, non-vascular roof of the extra- 

 embryonic coelom. 



