Plate VII. 



Arabic numerals placed between every two sections indicate the number 



of sections that intervene between those two (exclusive). 



Certain marks on the left of each section are for the identification of the 



sections and do not concern the reader. 



Series IX. a~n, — Sections through au embryo of Chelonia caouana with about 16 

 mesoblastic somites, taken ont lOi days after deposition. Surface views 

 given in Figs. 8 (PI. I) and 8« (PI. II). For detailed description see p. 

 53. CCx2. (Bi2.f) 



Sedgwick ('92) Fig. 1 — Embryo of Sq/lUiim canicida, 1h mm. in length. The hind 

 end of the embryo is notched. The medullary groove is just beginning. 

 The tail swellings of Balfour are well marked. (Sedgwick p. 585). 



Sedgwick (*92) Fig. 2. — Embryo of luija Î sp., 4 mm. in length. The medullary 

 groove is closed except at the hind end. The notched embryonic part of 

 the edge of the blastoderm has grown faster than the rest, and come to 

 project over the surface of the yolk. The sides of this projection are 

 already slightly bent ventral wards. They will eventually meet and form 

 the ventral part of the caudal region of the body (Sedgwick p. 585). 



