120 



SOME PROBLEMS OF CEIJ.-OK<JAX/ZAT/O.V 



The aniphiastral formation in alveolar protoplasm skives very clear 

 evidence aj^ainst the theory of fibrillar persistence. Here the fibrillar 

 rays can be seen growing out lhroii«;h the walls of the alveoli ^ cpiite 

 distinct from, thou«;h embeddeil in, them. At the close of mitosis 

 every trace of the fibrillar formation may disappear, r.i^. in echino- 

 derm-ej;i;s atter formation of the polar bodies, the protoplasm retain- 

 ing only a typical alveolar structure. 



Fig. 155. — .Stages in tlic first clc.iv.ii,'!- of the cpt^ in Cer,-hratnlii<i (.i-C. CnF.) and T^i.-i/.ir^fnrd 

 (D-/\ CiRIFFIN). 



A. First appearance of the cleavage-centrosome at the poles of the fused germ-nuclei ; cleavage- 

 astf-rs forming within the degenerating sperm-asters. B. Final anajihase of first cleavage, showing 

 persistent centrosomes and new asters forming. C. Immediately after division. D-F. Three 

 stages of the late anapluise in Thaliisseina, showing formation of new asters within the old. ( Cf. 

 Fig. 99.) 



The stronr^cst evidence a^^ainst fibrillar persistence is, however, 

 given by recent studies on mitosis, showing on the one hand that the 

 new astral centres do hot coincide with the old ones, on the other 

 that the old ravs degenerate /;/ situ, to be replaced by new ones. 

 Aside from many earlier observers, who believed the entire aster to 

 disappear at the close of mitosis, the first to assert the wholly new 



1 C/. Reinke r'95), Wilson ('99). 



