EXPLANATION OF PLATE XVll.—coudnued. 



the pedicle of invagination, from an embryo a little older than that of 

 fig. 17. 



EiG. 21. — Alimentary canal of an embryo about the age of that of fig. 8. 

 j)h. Pharynx, a. (Esophagus not yet open to pharynx, st. Stomach ; its 

 structure concealed and obscured by the adjacent gastrula-endoderm cell- 

 masses, i. Intestine, c. Its csecal termination, gt e. Two of the gastrula- 

 endoderm cells, now assuming the character of pellucid globules with super- 

 ficial granular networks, m. Branched muscular cell passing from the 

 body-wall to the latter. The intestine is seen to have a superficial tunic of 

 fusiform cells, and to be connected by such cells to the body-wall. 



Fig. 2'2. — Body-wall and some of the modified gastrula-endoderm cells, 

 from a stage between those of fig. 17 and fig. 8. ep. Epiblast. i^e. Tunic 

 of fusiform cells covering the pellucid bodies and their granular networks. 



Fig. 23. — Anterior part of the alimentary canal and body-wall, of same 

 age as fig. 21. ep. Epiblast. m t. Muscular tunic, m. Muscles, n g. 

 nerve-ganglion. 



