VALUE OF THE ATTRACTION-SPHERE. 



321 



nebenkern of the spermatocytes of Salamandra and Proteus 

 as the archoplasmic portion of an attraction-sphere. 



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Since that time it has been observed that a similar role 

 is played by the nebenkern in relation to the division of 

 spermatic cells in a great variety of animal forms, and we 

 are now probably justified in regarding the nebenkern as 

 always equivalent to the archoplasm of those cells in which 

 that structure was originally described. 



When a cell with a compound sphere, like the sperma- 

 tocyte of a salamander (Fig. V.), is going to divide, the 

 archoplasm becomes so fully used up in the construction ot 

 the central spindle, that there is no such residual mass left 

 round the centrosomes as in the mitotic figures of Ascaris 

 (cf. Figs. VII., IV.). In this way the external radial 

 envelope becomes directly related to the exposed half of 

 each centrosome, in such a manner as to be quite indis- 

 tinguishable from the protoplasmic radiations round the 

 centrosomes of a simple sphere (Fig. VII.). 



