476 WILSON. 



EXPLANATIONS OF PHOTOTYPES 5-8. 



Phototype 5. The " pause " (25 minutes), after complete fusion of the germ- 

 nuclei to form a cleavage-nucleus, and division of the aster. The focus is sharply 

 on one of the asters, showing the short beaded rays. In the specimen an ex- 

 tremely minute centriole can be seen in one of the asters, but this does not appear 

 in the photograph. 



Phototype 6. Late pause (30 minutes), showing initial stage in the formation 

 of the spindle and the differentiation of the nuclear reticulum. A group of centri- 

 oles is faintly shown in one of the asters (cf. Text-fig. IV, p. 451, Text-fig. V, 

 p. 452). 



Phototype 7. The karyokinetic figure just before the splitting of the chromo- 

 somes becomes apparent (42 minutes ; cf. Text-figs. VI, VII, pp. 454 and 458). 



Phototype 8. Anaphase (48 minutes), with the daughter-chromosomes lying 

 in contact with the large reticular centrosphere or centrosome. The astral rays 

 can be traced out into the cyto-reticulum, which is clearly shown. The spindle is 

 degenerating (cf. Text-fig. VIII, A, p. 461). 



