224 



EDWIN G. CONKLIN. 



the formation of a perfect spindle of small size. There can be 

 no doubt that the centrosomes of this spindle are derived from 

 the egg centrosome. The sperm nucleus is at this time far re- 

 moved from the egg nucleus and is closely surrounded by yolk ; 

 no astral radiations are found in connection with it, though one 



FIG. 5. 



FIG. 6. 



FIG. 7. FIG. 8. 



FIGS. 5-8. NaCl eggs of C. plana viewed from the animal pole ; the two polar 

 bodies are shown nearly over the spindles in the first three figures. In Fig. 5 the 

 sperm nucleus is still some distance from the egg spindle ; Fig. 6 shows an egg 

 spindle and a sperm spindle joined at one pole ; Figs. 7 and 8 show stages in the for- 

 mation of a tetraster from the egg and sperm spindles. 



or two granules which lie close to the nuclei may possibly 

 represent centrosomes (Fig. 4). 



Unfortunately a gap occurs at this stage in my material ; in 

 all the preceding figures (1-5) the sperm nucleus is small and 

 densely chromatic and is far removed from the animal pole ; in 

 the succeeding figures (612) the sperm nucleus has been re- 



