514 THEOPHILUS S. PAINTER 



shows a type of egg, perhaps some phase in the development of 

 those shown in the foregoing text figures, which is often seen. 

 The centrosphere has collapsed or become greatly flattened and 

 the bending of the rays is seen at one end. What the ultimate fate 

 of these eggs is I am unable to say. At the time the hving mate- 

 rial was being observed, I was not aware of the occurrence of eggs 

 of this type. Cases were noted here and there in the living ma- 

 terial in which the protoplasmic streaming was very severe and 

 it is possible that such eggs had the history shown in figures C 

 and D. 



The fate of the spiral aster eggs shown in figures 1, 2, 4, 6, 7, 

 and 8 seems to be a more or less normal cleavage. This conclu- 

 sion rests on the fact that in the living material those eggs which 

 shifted early from a monaster into an amphiaster divided nor- 

 mally. In one case only have I actually followed the division 

 with high power. That was in the egg treated with phenyl 

 urethane. It might be asked why these monaster eggs dividing 

 early were not followed more closely? It must be admitted that 

 at the time the experiments were being made, the points of great- 

 est interest were centered in those eggs which passed through a 

 complete monaster cycle. In the average experiment, one ob- 

 tains from 5 to 10 per cent of the egg showing the single aster 

 and of these, perhaps one in twenty shifts early into an amphi- 

 aster and divides. These cases were thus so rare that no attempt 

 was made to follow them under higher powers, in order to see 

 the condition of the astral rays. 



The stages with the twisted rays are found for a very short 

 time in both series studied. They appear when the controls are 

 shifting from the 2- to the 4-cell stage. No evidence of eggs 

 with bent rays has been found at any other period. That the 

 eggs which show spiral asters come from monaster eggs 

 which shift over into an amphiaster is clear from the following 

 considerations. 



When the monaster eggs are first seen in section the centro- 

 sphere is round. At a later period one finds the sphere elongated 

 and a careful study of such eggs has shown that a division of the 

 centrioles has taken place. A stage of this is shown in figure 9. 



