no Vertebrate Embryology 



the alimentary canal being now connected with the 

 cavity of the yolk-sack by a mere canal. The folds of 

 the amnion are spreading over the top of the embryo and 

 nearly meet. Each fold consists of two walls or limbs, 

 the space between which (dotted) is as before merely a 

 part of the space between the somatopleure and splanch- 

 nopleure. Between these arched amniotic folds and the 

 body of the embryo is a space not as yet entirely closed in. 



"^ represents on a different scale a transverse section 

 of E taken through the middle of the splanchnic stalk. 

 The dark ring in the body of the embryo shews the posi- 

 tion of the neural canal, below which is a black spot, 

 marking the notochord. On either side of the notochord 

 the divergence of somatopleure and splanchnopleure is 

 obvious. The splanchnopleure, more or less thickened, 

 is somewhat bent in towards the middle line, but the two 

 sides do not unite, the alimentary canal being as yet 

 open below at this spot; after converging somewhat they 

 diverge again and run outwards over the yolk. The 

 somatopleure, folded in to some extent to form the body- 

 walls, soon bends outwards again, and is almost immedi- 

 ately raised up into the lateral folds of the amnion af. 

 The continuity of the pleuroperitoneal cavity within the 

 body with the interior of the amniotic fold outside the 

 body is evident; both cavities are dotted. 



"G^, which corresponds to Z> at a later stage, is intro- 

 duced to shew the manner in which the allantois, now a 

 distinctly hollow body, whose cavity is continuous with 

 that of the alimentary canal, becomes directed towards 

 the amniotic fold. 



" In /T a longitudinal, and / a transverse section of 

 later date, great changes have taken place. The several 



