THE ACHROMATIC FIGURE 



157 



persists until they have reached opposite sides of the cell. In either 

 event it may fade out in its original position or first shrink inward before 

 the enlarging asters. In the literature are many reports of "a growth 

 of the astral rays into the nucleus" and "a lateral movement of the 

 central spindle into the nucleus." To what extent this may involve 

 a progressive alteration of extruded karyolymph beginning in the region 

 near the amphiaster is not clear, but the spindle figure in such cases at 

 least appears to incorporate structures not originally nuclear.^ 



With regard to the asters, it was shown by Chambers (192 1&, 1924) 

 that in living echinoderm eggs they are regions which are somewhat more 



•■C 



-;<•:■' 



'■J^:. 







^fS 





"f^:m 



Fig. 88. — Development of spores after last mitosis in ascus of Pustularia bolarioides. 



{After Bagchee, 1925.) 



solid than the rest of the protoplasm, but that their rays, instead of 

 being firm fibers as some had thought, are actually streams of fluid 

 passing inward through the more gel-like granular cytoplasm. This con- 

 firmed a widespread view that the aster is primarily an expression of 

 streaming movements in the cytoplasm. The rays merge into a central 

 mass of hyaline fluid which may in some cases begin to accumulate before 

 the cytoplasm becomes sufficiently gelated to reveal the centripetal 

 channels. The aster may sometimes show rather well-marked concentric 

 zones (Fig. 86) as well as one or more concentric series of granules about 

 the centriole. It is questionable how far these are normal appearances, 

 for Chambers (19176) asserts that some of them may be produced by 

 subjecting eggs to abnormal environmental conditions. 



During the anaphase the astral radiations remain conspicuous, but, 

 as the telophase progresses, they gradually fade from view, except in 



* See the discussion of these cases by Bleier (1931a). 



