ART. 1. — T. FUJITA. 



Y LiMAX (Meisenheimer) 



These tables show, that in most cases the mesoderm forma- 

 tion arises in the stage of the tenth generation of ectomere- 

 cells and at about the period when the cells number 50 or 

 more without any regard to the duration of time consumed in 

 their development. Further we learn that the genealogy of the 

 ectomere-cells up to the stage of the sixth generation follows 

 almost the same course, although the order of development some- 

 times varies with to species. And at the stage named, the diöer- 

 entiation of the germ-layers is first attained in some species. By 

 referring to the table it is furthermore evident that the amount 

 of deutoplasm present in the egg seems not to have any causal 

 effect on the rate of differentiation. In this respect, Ker'itina, an 

 egg rich in deutoplasm, forms the germ-layers in the same stage as 

 Li max, and S'q^honarla, which are scantily supplied with food-yolk. 



Before closing I wish to express here my deepest obligations 

 to Professors K. Mitsukuri and S. Watnsé for their kind super- 

 vision of the present work. 



