PLATE III. 



(Trionyx japonicusj. 



Fig. 16. — Dorsal view of an embryo of Trionix j'ipouictis, taken out 3i days after its 

 deposition. The amnion is just beginning to cover the bead. The 

 raednllary folds arisen except in the posterior portion, and still wide 

 open. See p. 17. JAx2. (126«) 



Fig. IGn — Ventral view of the same embryo. JA x 2. 



Fig. 17. — Dorsal view of an embryo of Trionyx Jajxmiciis, taken out 4 days after its 

 deposition. The amnion has covered a part of the head. The medullary 

 folds wide open, showing the sinus rlionihiAduUs in the posterior portion. 

 For further particulars see p. 17. A A x2. (136a) 



Fig. 18. — Dorsal view of an embryo of Trimn/x japnnicus, taken out 4 days after its 

 deposition. The head is now covered by the amnion. The medullary 

 canal is still wide open. See p. 17. Sections Series II [V\. IV). 

 JJx2. (136^) 



EiG. 19. — Dorsal view of an embryo of Tiin)n/.r Jaj>oitictis with 4 mesoblastic somites, 

 taken out 5Ä days after its deposition. The amnion covers the head and 

 neck region. The extra-embryonic cœlomic cavities appear wing-like on 

 l)oth sides of the anterior dorsal region. The medullary folds apposed 

 but not fused. See p. 28. Sections Series IV (PI. IV). AAx2. (128a) 



Fig. 20. — ^Dorsal view of the posterior two-thirds of an embryo of Triomjx japonifus 

 with 6 mesoblastic somites, taken out 6^ days after its deposition. The 

 amnion still leaves the larger part of the dorsal region exposed. The 

 medullary canal closed. See p. 29. A A x 2. (135) 



Fig. 21. — Dorsal view of the posterior half of an embryo of Tridinjx jupoiiieus with 7-8 

 mesoblastic somites, taken out 1\ days after its deposition. The amnion 

 leaves the posterior half of the dorsal region exposed. The medullary 

 canal closed. There is a slight artificial rent in the posterior edge of the 

 amnion, a little to the left of the median line. The white lines marking 

 the internal limits of the extra-embryonic cœlomic cavities meet over the 

 mid-dorsal region but diverge posteriorly. See p. 29. J.Jx2. (HI ffl) 



