76 



CELL-DIVISION 



in rank to the nucleus itself ; and we may conclude that every central 

 corpuscle is derived from a preexisting corpuscle, every attraction- 

 sphere from a preexisting sphere, and that division of the sphere 

 precedes that of the cell-nucleus." ^ Boveri expressed himself in 

 similar terms regarding the centrosome in the same year ('87, 2, 

 p. 153), and the same general result was reached by Vejdovsky 

 nearly at the same time,^ though it was less clearly formulated than 

 by either Boveri or Van Beneden. 



All these observers agreed, therefore, that the achromatic figure 

 arose outside the nucleus, in the cytoplasm ; that the primary impulse 

 to cell-division was given, not by the nucleus, but by the centrosome, 

 and that a new cell-organ had been discovered whose special office 



Fig. 29. — Final phases (telephases) of mitosis in salamander cells. [Flemming.] 



/. Epithelial cell from thelung; chromosomes at the poles of the spindle, the cell-body divid- 

 ing; granules of the "mid-body" or 7.imschcnkorper ■aX the equator of the disappearing spindle. 

 y. Connective tissue-cell (lung) immedtafely^after division; daughter-nuclei reforming, the cen- 

 trosome just outside of each ; mid-body a single granule in the middle of the remains of the 

 spindle. 



was to preside over cell-division. "The centrosome is an indepen- 

 dent permanent cell-organ, which, exactly Hke the chromatic elements, 

 is transmitted, by division to the daughter-cells. The centrosome rep- 

 resents the dynamic I'cntre of cell T ^ - 



That the centrosome does in many cases, especially in embryonic 

 cells, behave in the manner stated by Van Beneden and Boveri seems 

 at present to admit of no doubt ; and it has been shown to occur in 



1 '87, p. 279. 



2 '5. 



pp. 151, etc. 



3 Boveri, '87, 2, p. 153. 



