468 WILSON. [Vol. XI. 



sitory mid-body or Zwischenkorper) and are finally resolved 

 into a portion of the cyto-reticulum. 



5. The asters persist after cell-division and finally themselves 

 divide to form the daughter-asters which persist throughout the 

 ensuing " resting-stage." 



B. The Chromatin. — 6. A true reticular cleavage-nucleus 

 is formed by complete fusion of the two germ-nuclei. 



7. The amount of chromatin largely increases during the 

 "pause" following the fusion of the nuclei. At the close of 

 the pause a large part of the chromatin appears to be con- 

 verted into linin, and from this the spindle-fibres are largely 

 derived. 



8. The staining power of the chromatin is at a minimum 

 immediately after reconstruction of the daughter-nuclei. It 

 rapidly increases during the pause and reaches a maximum 

 when in the form of chromosomes. 



C. The Centrosomc. — 9. The central mass of the sperm- 

 aster, derived from the middle-piece, forms the centrosome (in 

 Boveri's sense) and at first contains no distinguishable centriole. 



10. The centrioles first appear in the daughter-asters derived 

 by the fission of the sperm-aster, and are probably formed by 

 endogenous differentiation. 



1 1. The centrioles represent the first stage in the formation 

 of a large reticulated erythrophilous centrosphere (centrosome 

 of Boveri). Whether this body represents the entire substance 

 of the original central mass (i.e., of the middle-piece) or only a 

 part of it is undetermined. 



12. At the close of division the centrosphere greatly de- 

 creases in size and finally divides to form the central masses of 

 the daughter-asters, in which the reticular structure is no 

 longer apparent. 



13. Centrioles are again formed endogenously in the daugh- 

 ter-asters and the history of the mother-aster is repeated. 



