32 



PRELIMINARY ACCOUNT. 



[CHAP. 



brane(a)is-the amnion proper, and the cavity within it, i.e. between 

 it and the embryo, is the cavity of the amnion containing the 

 liquor amnii. The allantois is omitted for the sake of sim- 

 plicity. 



It will be seen that the amnion a now forms in every direc- 

 tion the termination of the somatopleure ; the peripheral portions 

 of the somatopleure, the united outer or descending limbs of the 

 folds af in (7, D, F, G having been cut adrift, and now forming 

 an independent continuous membrane, the serous membrane, 

 immediately underneath the vitelline membrane. 



In / the splanchnopleure is seen converging to complete the 

 closure of the alimentary canal a' even at the stalk (elsewhere 

 the canal has of course long been closed in), and then spreading 

 outwards as before over the yolk. The point at which it unites 

 with the somatopleure, marking the extreme limit of the cleavage 

 of the mesoblast, is now much nearer the lower pole of the 

 diminished yolk. 



