PLATE I. 



( Clieloiiia cuoiunia.J 



Fig. 1. — Dorsal view of au embryo of Chdonia caouana taken out 91 days after its 

 deposition. The anterior amniotic fold is just beginning to rise, but 

 lias not yet covered the head. The dark median streak is caused chiefly 

 by the notochord. The medullary folds have arisen in the, neck-region. 

 The horse-shoe shaped opening in the posterior part is the blastopore. 

 For farther particulars see p. 17. Sections given in Series I (PI. IV). 

 Zeiss. rmx2. [B Uh) 



Fig. \a. — Ventral view of the same embryo. The prominent transverse fold in the 

 anterior part is the head. The ventral opening of the blastoporic passage 

 is quite large, aa x 2. 



Fig, 2. — Dorsal view of an embryo of Chelonia caouana taken out 10 days after its 

 deposition. The amniotic fold has now covered the lateral parts of the 

 head. The medullary folds have now arisen but are not closed. See 

 p. 18. aa X 2. (A 3a) 



Fig. 3. — Dorsal view of an embryo of Clidonia caouana, taken out 6^ days after its 

 deposition. The amnion has covered the anterior half of the embryo. 

 The medullary canal is still open at the posterior end. See p. 20. 

 aa X 2. (C 7a) 



Fig. 4. — Dorsal view of an embryo of Chelonia caouana taken out 6^ days after its 

 deposition. Two wing-like expansions on each side of the anterior dorsal 

 region are the extra-embryonic cœlomic cavities. The amnion covers 

 only the anterior half. The medullary canal is still open at the 

 posterior darkened portion. See p. 21. aa x 2. (C lb) 



Fig. 5. — Dorsal view of an embryo of Chelonia caourtna with 9 mesoblastic somites 

 taken out 9^ days after its deposition. The amnion has extended itself 

 over nearly the whole of the embryo, but leaves a small posterior portion 

 still exposed. Pari passu with the amnion, the extra-embryonic cœlomic 

 cavities have also enlarged themselves. They come near together in 



