18 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



the raid-piece of the spermazoon. In Figures 7 and 8 is shown the 

 beginning of that enormous growth which is so characteristic of the 

 early spermatocytes of all chilopods. 1 



In a former paper (Blackmail, :Ol) I laid stress upon this unusual 

 growth and called attention to the resemblance between the sperma- 

 tocyte in the vesicle stage and the female germ cell of a like stage. 

 The resemblance is indeed extraordinary, and extends in many respects 

 even to the most minute particulars. As the growth of the cell con- 

 tinues, the cytosome increases in size much faster than does the nucleus ; 

 whereas formerly, in the spermatogonium, the nuclear vesicle enclosed 

 the greater part of the contents of the cell, now it contains only a 

 relatively small portion. As is readily seen (Figs. 10-16), however, it 

 enlarges also. The cytoplasm during its increase in amount also changes 

 considerably in appearance. During the division stages of the sperma- 

 togonium it appears more or less granular with very fine fibrils in the 

 region of the centrosomes, while at other places it is finely reticular in 

 structure. As the growth continues, this reticulation becomes more 

 pronounced (Plate 8, Fig. 127), and at the stage of the completed 

 vesicle the network is often so coarse as to give the cytoplasm a ragged 

 appearance (Figs. 128, 130). 



As the cell grows, its appearance is also greatly modified by the 

 increase and arrangement of the archoplasm in a layer about the 

 nucleus of the cell (Figs. 15, 16, 128-130). The zones of archoplasm 

 of the two spermatocytes arising from one spermatogonium are further- 

 more connected by a bridge of fibrous character. This bridge is the last 

 trace of the interzonal filaments of the preceding division, and even in 

 the vesicle stage is often very distinct and well defined (Figs. 16, 128). 

 At the central portion of this mass of persisting spindle remnants the 

 small dark-colored bodies, often designated as the " Zwisehenkurperchen," 

 are generally shown distinctly (Figs. 13, 14). These are arranged in a 

 circle around the periphery of the bundle at the plane of constriction. 

 During the telophase of the subsequent division, the corresponding 



1 The author lias examined the five principal genera of Chilopoda, and all these 

 are characterized by an immense increase in the size of the spermatocyte over that 

 of the spermatogonium. This is slightly more marked in Lithobius than in Scolo- 

 pendra, Scutigera, and Geophilus, and is least noticeable in Scolopocryptops. In 

 the latter genus the cells are much smaller than in any of the others, but they are 

 still characterized by the relatively large amount of cytoplasm which is common to 

 all chilopods. It is my purpose to make a comparative study of the spermatocyte 

 changes of these genera of chilopods, and therefore I shall not enter into more 

 detail here. 



