454 



THEOPHILUS S. PAINTER 



times (fig. B 6 ), and the micromere which so often appears at 

 this time is present (Painter '15). 



This egg may be taken as typical in behavior in cases where 

 the aster does not undergo a marked retreat. The swelling of 

 the ectoplasmic layer and the movement of the protoplasm 

 are both seen but neither are severe. 



In figures Ci to C 6 the history of an egg is shown, where the 

 aster retreated only a short distance from the center. In figure 



Fig. B 



Ci the typical monaster egg is seen, as it was isolated at 11.17. 

 By 11.25 the chromosome vesicles were visible, and at 11.50 

 the aster occupied a position somewhat excentric to the center 

 of the egg. When the vesicles were forming a swelling of the 

 ectoplasmic layer was observed (fig. C 2 ) and in figure C 3 we 

 see the slight movement of the protoplasm. At 12.08 the 

 monaster reappeared (C 4 ) and at 12.25 the movement of the 

 protoplasm can be seen (fig. C 5 ). At 2.10 the egg had the 

 condition shown in figure C 6 . 



Figures Di to D 4 give the history of an egg in which the aster 

 retreated farther than in the two cases just described. The 

 swelling of the membrane together with the accompanying 



