574 VERA DANCHAKOFF 



Loeb considers the fragmentation of the nucleus as result of 

 the influence of too strong solutions and calls it amitotic disin- 

 tegration of the nucleus. If such nucleus fragmentation takes 

 place at a time, when chromatic basophilic substance is still pres- 

 ent in the cytoplasm, every nuclear part continues to exert at- 

 traction of the chromatic substance, and the latter accumulates 

 around every little part of the achromatic nuclear substance 

 (figs. 20, 22). In such cases many isolated radiations may ap- 

 pear around the nucleus particles. They are formed by centri- 

 petal currents, and are similar to the single radiation in the fer- 

 tilized egg. In some of the eggs there could not be traced in the 

 whole series of sections any noticeable part of the nucleus, and 

 yet their cytoplasm contained many cytasters. Should we con- 

 clude in such cases that the substance of the achromatic nucleus 

 has been scattered by the violent action of the chemical agent 

 through the cytoplasm in the form of small particles, and that the 

 cytasters developed around them? Much less evident are at 

 this time the changes connected with the structures, which 

 correspond to plastosomes. 



5. FIRST CHANGES IN THE EGG NUCLEUS AFTER FERTILIZATION 

 AND IN PARTHENOGENESIS 



The small achromatic nucleus, as shown above, seems to exert 

 strong attraction of the chromatic basophilic substance, which 

 is followed by its displacement. The next changes in the mutual 

 relationship of the achromtic nucleus and the basophilic sub- 

 stance of the cytoplasm are more conspicuous and therefore 

 easier to study in parthenogenetic eggs. 



The normally fertilized eggs present at this time the complex 

 picture of the union of two pronuclei, and, at least in some cases, 

 the egg pronucleus at once gets a considerable amount of chro- 

 matic substance from the spermatozoon (figs. 14, 15, 17). On 

 the contrary, parthenogenetic eggs show, step by step, the 

 gradual development of chromatin and chromosomes in the 

 nucleus. Moreover, parthenogenetic eggs often show certain 

 anomalies in the development of chromatin and chromosomes, 

 which may greatly facilitate its interpretation. Therefore a 



