70 K. MITSUKURI; 



a few cells. The two sections followini^ // show similar 

 groups of enteric cells. 



is the fourth section behind n. There is no trace whatever 

 of the enteron in this. For thirteen sections, tliis condition 

 continues ; then just for two sections, viz., on the four- 

 teenth and fifteenth sections behind o, of which — 



p represents the latter, there is a group of a few cells whicli 

 from their position and manner of deeper staining can be 

 nothing else than hypoblast cells. The cell-string again 

 disappears for seven sections. Then, on — 



q the eighth section behind p, the cell-grouj) again a|)pears 

 and this time is continued to the end of the tail, gradually 

 enlarofin"- in size as the followino; sections show.* 



r is twenty-three sections behind q. The hypoblast string is 

 slightly larger than in q. The upper part of the mesoblast 

 shows an arrangement like the mesoblastic somites but is 

 merged below with the indifferent mass, without any 

 limitation. 



S is eleven sections behind r. The hypoblast string is larger. 



t is fourteen sections behind s. The hypoblast m;iss is now 

 quite large and there is a lumen in its upper part. Tiie 

 mesoblast has largely acquired the epithelial arrangement, 

 but there is still a part below where stellate cells are scattered. 



u is nine sections behind t. In this section, there is no 

 longer any stellate cells below. The enteron is not 

 painted black from this section on. 



V is two sections behind n. The notochord and enteron 

 have united, as also the enteron and mesoblast below. 



w is the third section behind v. The medullary canal, the 

 notochord, and the enteron are now united and a narrow 

 slit riuming tln'ough the middle of the lirst two empties 

 into the relatively large enteric lumen. Tiiis can be no 

 other than the neurenteric canal. The enteron is united 

 below with tne mesoblast. 



* 'J'he scale of enlargement differs from this section onward. 



