;378 IsTaohide Yatsu. 



new formation and not due to reduction (p. 529, etc.). But it is 

 certain that the material for the new centrosome must come from the 

 old, as already mentioned. This endogenous formation of daughter 

 centrosome may well be called "moulting," in lieu of Boveri's re- 

 duction. So much for the controversy in interpretation. Vejdovsky 

 and Mrazek give another type besides that described under A. The 

 centrosome enlarges and the centriole which had been divided into two 

 acquires a ray system and a centrosome (Text Fig. B). The old cen- 

 trosome degenerates. In this type the centrosome never divides, but 

 is formed separate from the beginning. Example: formation of the 

 second cleavage centrosomes in Glossiphonia (=Clepsine) (Vejdov- 

 sky and Mrazek, '03, in Cerebvatulus lactus, in SerpuJa (Soulier, '06, 

 pp. 458-459). A critical study of the literature will convince one 

 that this type of centrosome formation is the most prevalent of all ; 

 in fact all the known cases, except those mentioned under A and C 

 {vide infra) may, I think, be included under this type. Of course 

 in very few cases is the process carried out with diagrammatic clear- 

 ness as in Cerehmtulus. In most cases it is modified by various 

 irregularities. Of these three may be mentioned. 



(a) Owing to the precocious fading of the mother centrosome the 

 centriole becomes naked and divides into two. Around these the 

 daughter centrosomes are formed. Example, in the spermatocytic 

 division of Geopliilus (Bouin, '04). 



(&) The mother centrosome disappears after the centriole has 

 divided. Two naked centrioles exist for a time, as shown in Text 

 Fig. C. Example, the formation of the second maturation centro- 

 somes in Thysanozoon (van dor Stricht, '9S) and in T/imax (Byrnes, 

 '99). 



(c) The centriole divides and before the separation of the daughter 

 centriole a connnon centrosome is formed around them. After it 

 has enlargel two grand-daughter centrosomes appear within it (Text 

 Fig. Ill B.). Erlanger's account ('98) of the Q^g of Spliaerech- 

 i)ius may conform to this process. It is doubtful whether or not 

 Griffin's case of Tlialassema re])reseuts tyi)e A, for the reason that he 

 actually figures an enlargement of centrosome. Might it not be the 

 case that the daughter centrosome disappears in the mother centre- 



