588 VERA DANCHAKOFF 



chromosomes are usually very rudimentary and the spindle itself 

 is small. 



It is only natural that, anomalies in the development of the 

 spindle be accompanied by anomalies in the centrosphere, since 

 the centrospheres appear as parts of cytoplasm, in which the rays 

 of the bipolar radiations converge and from which the threads of 

 the spindle are growing into the nucleus. With the regular 

 flowing of the archoplasm to the whole circumference of a spher- 

 ical nucleus, no centrosome will differentiate, a condition which 

 occurs in the case of a monaster. With several irregular ac- 

 cumulations of the plastosomes around the nucleus, several 

 rudimentary centrosomes arise at once. With the development 

 of a small spindle without cytoplasmic radiation no centrosomes 

 are seen on their poles. These cases of development of spindles 

 without centrosomes recall the mitotic figures of the plant cells. 



The further division stages consist, according to the usual 

 description, in simultaneous enlargement of the centrosomes, 

 shifting of the chromosomes, and in the consecutive changes of 

 the chromosomes in vesicles and in their mutual fusion into 

 daughter nuclei (figs. 29, 30 and 31). The daughter nuclei again 

 appear achromatic (fig. 31). This must depend upon chemical 

 changes in the substance of chromosomes, yet it is not possible 

 to determine, whether these changes depend merely upon ab- 

 sorption by the chromosomes of certain substances from the 

 cytoplasm or whether a reciprocal exchange of certain substances 

 between them and the cytosome is involved. The ultimate fate 

 of the spindle substance is more or less definite. The spindle 

 fibers, like the chromosomes, experience equal division and soon 

 afterwards disperse themselves uniformly in the cytoplasm of the 

 two daughter cells. 



At the time of the reconstruction of the daughter cells the 

 cytoplasm divides. Around the achromatic daughter nuclei 

 single radiations arise, which again are visible manifestations 

 of cytoplasmic currents and which contribute to a re-grouping 

 of different substances in the cell. These currents are directed 

 toward the nucleus. The attraction exerted by the two daugh- 

 ter nuclei creates a zone in the cytoplasm of the egg, in which the 



