602 GRIFFIN. [Vol. XV. 



centrosphere between the rays and gradually replaces the latter. 

 By the early anaphase, during the peripheral wandering of the 

 centrosomes, the centrosphere has assumed a strictly reticular 

 appearance, as described by Wilson and others in the Echino- 

 derms (PL XXXIII, Figs. 41, 42). 



This progressive development of the reticulum pari passu, 

 with decrease of rays within the centrosphere, and following 

 close upon metaphase, constitutes strong evidence that the 

 reticulum is developed out of the substance of the rays ; and 

 this evidence is all the stronger from the fact that both rays 

 and reticulum stain exactly the same. We have here a radial 

 structure breaking up into a reticular one. But in cells of this 

 type the radial structure is indicative of mitotic activity, the 

 reticular of repose (" resting " condition). These considera- 

 tions lead us to the view that the reticular centrosphere is a 

 degeneration phenomena consequent upon the withdrawal (or 

 cessation of activity) of the centrosome to initiate a new system, 

 and heralds the breakdown of the astral system. From now 

 on, the old system with its rays actually does disintegrate. 

 Evidence drawn from comparison of other forms lends addi- 

 tional support to this view, for in all cases, as far as I know, 

 the reticular centrosphere is secondary and preceded by stages 

 in which the rays focus directly to the centrosome or its more 

 hnmediaie envelopes.^ 



The enormous number of rays in the dense astral crown 

 during anaphase renders it impossible to regard them as entirely 

 consisting of rearranged cyto-strands, as Wilson and others have 

 so interpreted them. As there is obviously insufficient material 

 in the preexisting cyto-reticulum for this purpose, we are forced 

 to look upon them as in part a new formation. The additional 

 material is probably derived as a product of some specific form 

 of metabolic activity set up by the centrosome, while their 

 radial arrangement is most likely due to a radial disposition of 

 the forces thereby disengaged, more or less analogous, though of 

 course not strictly comparable, to the magnetic "lines of force." 



' Cf. Sea-urchins (Wilson, Kostanecki, and others) ; Nereis (Wilson) ; Chae- 

 tofterus (Mead) ; Triton (v. d. Stricht, '92) ; Trout (Henneguy, '91) ; Rhynchelmis ? 

 (Vejdovsky), etc. 



