RECORDS 123 



was brought forward that the cleavage centrosomes of the pri- 

 mary division figure arise by the division of a single primary 

 centrosome that is formed outside, but immediately upon, the 

 nuclear membrane. As regards the chromatic transformation 

 of the nucleus, two types of chromosome formation were de- 

 scribed. In both cases a large nucleolus is formed, which at- 

 tains a much greater size than in the fertilized eggs. In one 

 type this nucleolus remains a plasmosome, or true nucleolus, 

 which fades away at the time of division, the chromosomes aris- 

 ing nearly in the usual manner from the chromatin network. 

 In the .second type, the entire chromatic content of the nucleus 

 is gradually accumulated in the nucleolus, which thus forms a 

 chromatin-nucleolus from which the chromosomes are afterwards 

 derived nearly in the same manner as in Spirogyra. 



In regard to the accessory asters, or cytasters, it was shown 

 that they contain central bodies often indistinguishable in sections 

 from the centrosomes of the nuclear figure, though in many 

 cases less well developed. Sections demonstrate that the divi- 

 sion of the cytasters is preceded by division of the central body, 

 which draws out to form a central spindle in a manner similar 

 to that described by MacFarland in the eggs of gasteropods. 

 This fact, taken in connection with the physiological activities 

 of the cytasters seems to remove every doubt regarding the 

 identification of the central bodies as true centrosomes. 



In comparing the phenomena in the magnesium eggs with 

 those of normal fertilization, it was pointed out that the forma- 

 tion of accessory asters at the time of fertilization or cell divi- 

 sion, is a widespread phenomenon. In normal fertilization or 

 division, the accessory asters are of a very transient character. 

 In the magnesium eggs they attain a much greater develop- 

 ment both structurally and functionally, but they are probably 

 to be regarded as differing only in degree from those which ap- 

 pear during the normal process. In all cases their disappear- 

 ance is probably due to a concentration of the protoplasmic activ- 

 ities about the more active centres, connected with the nucleus, 

 which alone survive to perform the normal functions of division. 

 Evidence was adduced that the nuclear transformation occurring 



