PLATE LXXVII. 



Fie. j&j.-Sertion of the posterior part of the body of the embryo of the chick at the forty-eighth honr. 

 . Central nervous system. 1,. Proto-\vrtrbrro. c. Chord I dirsulis. d. Upper or corneal layer, e. Serous, and/, 

 ventral lamina. ,/. Wolllian duct. /. Aorta;. i. Pleuro-peritoneal cavity. k. Lower layer. D. [ntestinal 

 furrow. A. Ainniotic fold. 7. Blood-vessels. 



Pin. 183. Section of anterior cerebral vesicle of embryo at the middle of the fecund day. a. Cavify of 



anterior cerebral vesicle. /'. Wall of reivl -ral ve-irle. r. I'rimary opt it- vesicle, and ,1 its wall. . 



layer of gerin. /. Tliickenins of th.- upper layer for the formation of (be 1,-ns. ,,. Middle layer. /.. .V.TPU* 

 opticia. p. 157. 



