306 Naohide Tatsu, 



1. Asters having the power of division arise in the cytoplasm 

 independent of the nucleus. These asters first appear simul- 

 taneously in situ scattered through the cytoplasm and, though 

 plainly visible in the living eggs, show no evidence of genetic 

 connection with one another. At a later period, however, they 

 multiply by division synchronously with the division of the 

 nuclear asters. 



2. At first vague clear spots appear in the cytoplasm, which 

 gradually become surrounded by radiating lines ot granules and 

 finally assume the form of asters. In sections central granules 

 appear in the accumulations of hyaloplasm and afterward rays 

 are formed about them. 



3. In the cytasters there is a central granule W'hich is a true 

 centriole formed de novo in cytoplasm. The central bodies divide 

 as in the ordinary asters and thus give rise to the centers of the 

 daughter aster. Sometimes two centrioles are found in a cen- 

 trosome (p. 561). 



4. In enucleated fragments obtained by shaking the unfer- 

 tilized eggs and treated with MgClj the typical cytasters often 

 containing the centrioles are found. Moreover, these asters may 

 multiply by division (p. 581). 



Wassilieff ('02) made interesting experiments on the egg of 

 Strongylocentrotus lividus. The centriole, he claims, is formed 

 by the interaction of the nuclear fluid and cytoplasm. "Der 

 Kern sondert in das Protoplasma eine gewisse Substanz ab, 

 welche zur Bildung eines Centrums in Protoplasma Veranlas- 

 sung giebt und um dieses letzteres herum lagert sich die pro- 

 toplasmatische Strahlung ab " (p. 769). I perfectly agree with 

 him, so far as this conclusion is concerned, though his evidence 

 was not strong enough to establish it. Moreover, he fails to 

 consider what seems to be of prime importance; he insists that 

 the nuclear fluid flows out as the egg nucleus fades. If so, why 

 should the cytasters in some cases appear, while the egg nucleus 

 is intact? He states that the cytasters must have originally been 

 connected with the nuclear aster. To bear out this view he gives 

 a case in which a cytaster is connected with the nucleus. The 

 connection seems to me to be merely secondary one. He raises 

 objections to Wilson's results on the formation de novo of the cen- 

 trioles in the enucleated fragments obtained by shaking on the 

 ground that if the eggs are so violently shaken that they break 



