3G4 



Naohide Yatsii. 



a 



c 



d 



f g k 



J 



Fig. a. Diagram showing tlio size relation between tbe cell and centrosome. 

 The vertical lines represent diameters of cells taken from embryos of various 

 stages (all at tbe nietapbase). X 1*506. Below, tbe outlines of tbe centrosome 

 of corresponding cells are indicated. X 1666. a — 1-cell stage, b — 4-cell stage, 

 c — 8-cell stage, d — 64-cell stage, e — 32-cell stage, f — "placula" stage, g — blastula, 

 h — gastrua (a cell of the apical organ), i — young pilidium (an entoderm 

 cell), n — pilidium (an entoderm cell), k — pilidium (an entoderm cell near 

 tbe mouth). During the process of reproduction tbe centriole of e has become 

 smaller and that of k larger than those in the original drawing. 



