302 



ISfaohide Tatsu, 



had been developed to a fairly large size. (Fig. 13a.) The 

 nucleated half of the same egg was stained and the mitotic figure 

 was found intact. (Fig. 13b.) The enucleated fragment was 

 cut into sections. The general character of the cytoplasm is 

 very similar to that of Fig. 7, while the large aster (Fig. 14a) at 

 the center shows totally diflPerent features from any other that 



J2 a 



12 b 



X 



I'^a 



13 b 



JFiG. Wl (X330). 



I2a and h, Enucleated fragments containing cytasters produced by CaCl2 solution, time-sterilization. 

 I^a, enucleated fragment with cytaster produced by MgCb solution, heat-sterilization. J^h, nucleated 

 fragment from the same egg as i ?a, stained with acetocarmine. 



come under my examination. The center (centrosome .^) is elon- 

 gated; no central granules could be made out. Around this 

 center long strong rays radiate. They look very brittle, judging 

 from the fact that some rays show jagged broken edges. For 

 comparison I reproduce a central maturation aster (Fig. 14b) 

 from an entire egg kept in 3.5 per cent solution of MgCU in sea- 



