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ROBERT CHAMBERS. 



fragment becomes multi-nucleated but remains unsegmented (Fig. 

 23-c). Non-nucleated fragments of eggs in a later stage (stage 

 d} proceed somewhat farther (Fig. 24). The multi-nucleated 

 masses arising from them make several periodic attempts at seg- 

 mentation (Fig. 24-^). Small furrows appear over the surface 

 of the egg, cutting in between the peripherally arranged nuclei. 



Q 



Fig. 23 



FIG. 22. Starfish egg in stage corresponding to b in Fig. 6 cut into two 

 fragments^ The non-nucleated fragment contains no material from the 

 germinal vesicle and is nonfertilizable. 



FIG. 23. Starfish egg in a later stage corresponding to c in Fig. 6 cut 

 through the nuclear area. The cytoplasm in the injured nuclear area disin- 

 tegrated leaving a non-nucleated fragment, b. That the fragment is fertiliza- 

 ble is shown in c by the formation of a fertilization membrane and the re- 

 peated division of the sperm nucleus. The fragment, however, is unable to 

 segment. 



FIG. 24. a, starfish egg in stage d of Fig. 7 cut into a nucleated and non- 

 nucleated fragment, b, both fragments fertilized. The nucleated fragment 

 segmented in the normal way with a number of blastomeres.. The non- 

 nucleated fragment became multinucleated and furrows appeared over its 

 surface in an attempt at segmentation. 



