52 K. MITSUKURI. 



Fhj. 32. — Directly beliiiul the dosai openiug of the blastoporic passage. 



Figs. 83-36. — Selected transverse sections from the anterior part of a Clenimys 



embryo very similar to Fig. 4 aiid from the same deposit. Introduced to 



show the manner of separation of the three structures : the notochord, the 



mesoblast and the gut-hypoblast. Fig. 33, BB x 4, Figs. 84-3G, DD x 2, 



(XXXXVIU). 



Fig. 5-5.— Through the head-fold. 



Fig. 34. — Second section behind. 



Fig, 35. — Second section behind. 



Fig. 36. — Fifth section behind. 

 Figs. 37-38. — Two transverse sections from a Trionyx embryo IY2 days old. 

 DDx2. (127). 



Fig. 37. — Is more forward. The gut-hypoblast is at some distance from 

 the c\\oxi\\x-anlage and the median line. 



Fig. 38. — The gut-hypoblast has extended itself inwards to the chorda-rt/j/rt^re. 

 Figs. 39-40. — Sections of Amphioxus. From Hatschek, after Hertwig. 



