572 VERA DANCHAKOFF 



genesis, it proceeds in the latter case much more vigorously and 

 leads to such peculiar formations as the artificial cytasters. 



Every investigator, who has studied artificial parthenogene- 

 sis, is familiar with the appearance of cytasters. Morgan 

 described them in 1896, '99, and '90; Wilson in 1901. Accord- 

 ing to Wilson, they may be found in different parts of the cyto- 

 plasm. The primary radial arrangement of the cytoplasm 

 around the nucleus in such cases is less strongly marked. These 

 cytasters may function as centers for division, but no full divi- 

 sion of cytoplasm occurs around cytasters, which do not contain 

 chromosomes. The cytasters may contain in their centers deeply 

 stained central corpuscles. Wilson identifies the central cor- 

 puscles of the cytasters with true centrosomes and concludes, 

 like Morgan, that both of them are formed de novo. It is well 

 known what a severe protest this opinion drew from Boveri. 

 According to Boveri, Morgan in his experiments obtained, be- 

 sides transitory artificial astrospheres, which does not partici- 

 pate in mitosis, only pathologically multiplied ovocentra and 

 their derivatives. Fischer and Oswald explain the formation of 

 astrospheres during artificial parthenogenesis through a coagu- 

 lation produced by withdrawal of water. 



The relation of the cytasters and the centrosomes will be dis- 

 cussed later. At present merely the origin of the artificial 

 cytasters will be studied — as judged by the conditions found in 

 my preparations. 



As mentioned above, the chromatic basophilic bodies become 

 labile, impregnate the surrounding protoplasm and cause the 

 network of cytoplasm to be more intensely stained around them. 

 The single meshes of the cytoplasm become thereby thicker and 

 appear sometimes in the form of a few radiations, directed toward 

 the basophilic centers. This may be observed occasionally in 

 normally fertilized eggs, in which the basophilic substance is 

 gradually transported to the remote parts of the cell. Should 

 the dissolution of all the chromatic masses in parthenogenetic 

 eggs occur rapidly and simultaneously, the rapid flowing off of 

 this substance will at the same time transfonn numerous meshes 

 into radial strands (fig. 5). As in normal fertilization, this sub- 



