366 Naohide Yatsu. 



a view quite different from what has been said above. The diplo- 

 some, found in the tisaue-cells and in the germ-cells before their 

 growing period, she identifies as the centrosome.^'^ This structure 

 divides bodily into two in spermatogenesis and during the oogonial 

 divisions, while in oocytic divisions "durch inner e Dijferenzierung'^^ 

 wird das zuerst kompakte Cytocentrum (=diplosome) in eine Hohl- 

 kugel umgebildet, und in der Mitte derselben, kommt ganz all- 

 mahlich ein winziges Kornchen zum Vorschein, das sich wahrend 

 der Metamorphose in zwei Kornchen teilt" (pp. 302-303). These 

 granules she calls centrioles. From this she concludes that the cen- 

 trosome is a permanent cell-organ and the centriole is not, because 

 it is not present in all the division stages and occurs only in large 

 cells. If one studies her paper critically, it will not be difficult to 

 see that this conclusion rests first upon the fact that in Enterox- 

 enos the common type of aster-division is peculiarly modified by 

 the growth of the centriole; and second, upon a misinterj)retation 

 of the nature of the diplosome. It cannot be denied that the small 

 granules in her Figs. 7 and 13 (text Fig. D on p. 315) are mor- 

 phologically as well as physiologically the same as those at the centre 

 of the centrosome of Fig. 1. Tlic distinction hetiveen the centro- 

 some and centriole is, after all, not a question of position, hut 'of 

 morphological structure. But, on the other hand, it may be argued, 



'"It is interesting to note tliat Boveri admits tliat in some oases tlie diplosome 

 may represent centrioles and not centrosome ('00, p. 201). Meves ('02) and 

 ttie Shreiners ('00, p. 348) seem to have misinterpreted Boveri. 



"The centriole must have arisen in the centrosome or division centre during 

 the course of phylogeny. Yet from this it does not necessarily follow that at 

 the present time the centriole is formed from the centrosome. As a matter of 

 fact there exists a naked centriole, and in no cases ever described does the cen- 

 trosome precede in its formation the centriole. The appearance of the segmen- 

 tation centrioles after temporary disappearance cannot be called inner differen- 

 tiation, because they keep their identity during this period. The question natur- 

 ally arises as to whether or not there is a centrosome destitute of centriole. 

 Excepting the cases in which the absence of the centriole is due to a failure 

 in technique and the centrosome from which the cleavage centriole has gone 

 out of sight, the centrosome without centriole has actually been observed in a 

 few forms at one or both ends of the maturation spindles, such as Entroxcnos. 

 Zooffnm(ft. The disappearance of the centriole in these cases, however, may be 

 due to its precocious degeneration. 



