446 WILSON. [Vol. XI. 



entirely independent of the "gewohnliche Fadenwerk der Zell- 

 substanz." 



My own observations compel me to differ widely from Boveri 

 on this point, and lead to a view which on the whole agrees 

 with that of Heidenhain and Reinke, though differing from 

 both in some important particulars. In Toxopneustes there is 

 the strongest evidence that the astral rays developed about the 

 middle-piece of the spermatozoon arise by a direct transforma- 

 tion or morphological rearrangement of the preexisting cyto- 

 reticulum, and that they grow at their outer ends, as the 

 sperm-aster moves through the egg-substance, by progressive 

 differentiation out of this reticulum. The spindle-fibres are 

 formed in like manner out of the intra-nuclear achromatic net- 

 work (linin); and my observations show conclusively, I think, 

 that at the close of karyokinesis the greater part of the spindle- 

 fibres are resolved into that portion of the general cyto-reticu- 

 lum that lies between the two daughter-nuclei and takes no 

 part in the formation of the succeeding amphiaster. 



My observations indicate, furthermore (though the evidence 

 is not conclusive), that the intra-nuclear network (linin) from 

 which the spindle-fibres arise is in large part derived directly 

 from the chromatin. If the latter view be well founded, a 

 direct morphological continuity can be traced between chro- 

 matin, linin, archoplasm, and the cyto-reticulum. 



Observations. 



A. Origin, Stnictnre, and Growth of the Sperm-aster. — The 

 entrance and rotation of the sperm-head have been sufficiently 

 described in my former paper.^ A few moments after entrance, 

 in favorable sections, the middle-piece may be distinctly seen 

 as a rounded body lying at the base of the sperm-nucleus, from 

 which a broad granular entrance-cone extends outwards towards 

 the periphery, as in Fig. \, A. At this period no radiations 

 are present in the surrounding cytoplasm, which has the 

 appearance of a reticulum along the fibres of which are scat- 

 tered minute granules or "microsomes." These, like those of 



Journal of Morphology, X, i, 1S95. 



