452 



THEOPHILUS S. PAINTER 



and figs. 7, 8) which eventually result in a separation of the two 

 blastomeres, and frequently also, in the formation of a third 

 (enucleated) ball, which may or may not fuse again with one 

 of the blastomeres. We witness here again, during this divi- 

 sion cycle, the formation of pseudopod-like processes (fig. 7) 

 especially on the side farthest away from the spindle. Also, 

 the two sister blastomeres become fully separated (fig. 8) when 

 cleavage finally takes place. 



Eventually the two blastomeres round up and the third 

 division cycle sets in. The further history of these eggs has 

 been described elsewhere (Painter, '15). Isolated eggs have 

 given me some normal plutei. Boveri ('05) obtained the same 

 results. 



Fig. A 



In a few monaster eggs, triasters and tetrasters are obtained 

 at the second division cycle. As far as they were followed, 

 they did not differ in their behavior, from dispermic eggs, and 

 eggs isolated did not develop normally. 



At the second division cycle the last two types of eggs men- 

 tioned on page 449, under c and d, can not be distinguished. 

 One finds the reappearance of a single division center; this, 

 however, is marked by the small size of the centrosphere, which 

 rarely approaches, in my experience, the size of the monaster 

 in the first division cycle. After a variable length of time, 

 movements of the protoplasm set in which are essentially like 

 those seen in the first division cycle of the monaster eggs except 

 that the activity is not confined to one side of the egg but in- 

 volves the whole or nearly the whole surface (fig. 6). Very 

 frequently a rough division of the egg separates two blastomeres, 

 (rigs. F 5 , F 6 , or F 7 ) but this is accompanied by a great deal of 



