BLACKMAN: THE SPERMATOGENESIS OF SCOLOPENDRA. 33 



somes, where they are arranged in a very irregular manner (Figs. 31, 

 32). There is no true equational plate established, for the chromosomes 

 are not arranged in one plane at any period of mitosis. 



The spindle as established in the large type of spermatocyte has a 

 very constant and definite relation to the long axis of the cell and of the 

 testis. In all cases observed, it is perpendicular to the long diameter of 

 the cell, and as the cells are always arranged parallel to the follicle, the 

 spindle as first constructed is perpendicular to the long axis of the testis. 

 The constancy with which this arrangement of the spindle occurs at this 

 stage suggests that the cell may have a distinct polarity in the early stages 

 as well. But this is not entirely the case. While there is a very definite 

 relation between the ZwischenkiJrper and the nuclei of the two connected 

 cells, this does not extend to the other organs of the cell. The centro- 

 some with its surrounding substance may apparently be situated at any 

 point within the outer zone of archoplasm. However, during the early 

 prophase it often so arranges itself upon the side of the nucleus opposite 

 the persisting spindle, that a plane passed through these two structures 

 divides the nucleus and the cell body into two approximately equal 

 parts (Figs. 16, 17). Even at this stage, however, the karyosphere is 

 not involved in this polarity of the cell contents, but may apparently 

 occupy any position relative to the plane of division. 



As the spindle is formed, several interesting changes in the cytosome 

 take place. The cell outline formerly cone-shaped rounds off until it is 

 in the form of a more or less regular oval (Figs. 30, 31, 32). The 

 cytoplasm also undergoes interesting changes. The inter-reticular sub- 

 stance in the proximity of the nucleus loses the dense appearance which 

 it had assumed during the prophase and again takes on its characteristic 

 structure. As the subsequent stages of mitosis proceed, this return of 

 the cytoplasm to its normal reticular condition continues, until finally, 

 in the late anaphase, it has entirely resumed its habitual character. 

 These changes are due to the loss on the part of the cytoplasm of that 

 staining capacity characteristic of it during the prophase. It is very 

 important to note that while the cytoplasm is assuming its wonted ap- 

 pearance fundamental changes are apparent in other elements of the 

 cell. The astral radiations, which during the prophase are not excep- 

 tionally well marked, increase rapidly during the metaphase and ana- 

 phase, until at the conclusion of the latter stage they apparently permeate 

 every part of the cell. This growth of the astral systems does not occur 

 at the expense of the cytoplasmic reticulum, for, while this network is 

 indeed somewhat obscured by the astral fibres, it is still present and of 



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