BLACK.MAX: THE SPERMATOGENESIS OF SCOLOPENDJiA. 101 



Toxopneustes (Wilson, '95 1 ', :01 l , :01 b ) at various stages. According, 

 then, to Boveri's own criteria — i.e. the persistence of the body and its 

 relation to the astral systems — I believe lam justified in identifying the 

 small deeply staining body at the centre of the asters as n c< ntrosome. The 

 only characteristic which does not fit into his definition of the centrosome 

 is the time of division. When the great variation in the morphological 

 characteristics exhibited by this organ indifferent cells is considered, and 

 the great variation in the physiological processes as well, 1 believe that 

 no conclusions of such fundamental importance as the identification of 

 this element should be based upon its time of division. 



I am convinced that the less dense sphere surrounding this centro- 

 some, which I have called the centrosphere, represents a different sub- 

 stance. It is probable, according to my observations, that this substance 

 is a reserve supply of archoplasm in a highly condensed form. This 

 archoplasmic material is of a similar nature to the ordinary archoplasm 

 of the cell during that period of the prophase in which it is apparently 

 dissolved in the hyaloplasm, except that it is probably in a more con- 

 centrated form. This centrosphere substance is used when occasion 

 demands in the formation of new fibres or in the elongation of those 

 already formed. Appearances which strongly support this conclusion 

 may be observed in the first mitosis of the small type of spermatocyte, 

 where the centrosphere is large and conspicuous, while in the succeeding 

 stages it is very much smaller. During the interim the centrosonies 

 have moved apart and the spindle has been modified in such a manner 

 as to give rise to the apical point. Considerable of the reserve archo- 

 plasm contained in the centrosphere has evidently been withdrawn from 

 this structure and has been used in the production of the set of fibres 

 connecting the centrosome and the apical points. Furthermore in the 

 telophase, when the chromosomes have been drawn apart and are col- 

 lected in masses at the opposite ends of the cell, the centrosphere again 

 increases in size. This is evidently accomplished by the retraction of 

 the mantle fibres and their conversion into latent archoplasm. 



This is the only way in which I can interpret the observed facts, and 

 if this explanation is correct, the centrosphere should not be considered 

 a component part of the highly specialized centrosome, but should more 

 properly be classed with the less differentiated archoplasm. These 

 observations, while in themselves quite different from those of Lillie 

 (*98), would seem to lead to the same conclusions that he reached in 

 studying the formation of the second polar spindle in the egg of Unio. 

 He observed that the second maturation spindle arises from the material 



