The Development of the Chick 1 1 1 



folds of the amnion have met and coalesced above the 

 body of the embryo. The inner limbs of the several 

 folds have united into a single membrane (a), which en- 

 closes a space (ae or ac) round the embryo. This mem- 

 brane (a) is the amnion proper, and the cavity within it, 

 /". e. t between it and the embryo, is the cavity of the 

 amnion containing the liquor amnii. The allantois is 

 omitted for the sake of simplicity. 



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

 direction the termination of the somatopelure; the per- 

 ipheral portions of the somatopleure, the united outer or 

 descending limbs of the folds of in (7, Z>, F, G having 

 been cut adrift, and nov forming an independent con- 

 tinuous membrane, the serous membrane^ immediately 

 underneath the vitelline membrane. 



" In /the splanchnopleure is seen converging to com- 

 plete 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 somato- 

 pleure, marking the extreme limit of the cleavage of the 

 mesoblast, is now much nearer the lower pole of the 

 diminished yolk. 



" As a result of these several changes, a great increase 

 in the dotted space has taken place. It is now possible 

 to pass from the actual peritoneal cavity within the 

 body, on the one hand round a great portion of the cir- 

 cumference of the yolk, and on the other hand above 

 the amnion , in the space between it and the serous 

 envelope. 



" Into this space the allantois is seen spreading in K 

 at al. 



