1902.] NICHOLS — SPERMATOGENESIS ONISCUS ASELLUS LINN. 91 



plasmic fibres equals that of the nuclei. I cannot be certain that 

 this is invariably the case. With the iron ha^matoxylin stain the 

 bundle of cytoplasmic fibres stains deeply, like the nucleus, and it 

 is therefore impossible to distinguish between them in cross section 

 where both appear. The delicate fibril previously mentioned, 

 which joins the nucleus, stains faintly and can therefore be distin- 

 guished from the nucleus. In Figs. 8i and 82 cross sections of 

 sperm colonies at slightly different stages of development, colored 

 with this stain, are compared. In both images may be seen similar 

 to that of Fig. 80 — /. e., a circle of dots merging into faintly stain- 

 ing fibres. Sometimes the latter have a granular or beaded struc- 

 ture (Fig. 8i«). These are sections near the anterior end of the 

 colony, and here again the central circle of dots, representing the 

 posterior cytoplasmic fibies, is lacking. Fig. 82/^ represents a sec- 

 tion which I interpret as having been cut slightly posterior to Fig. 

 82^. The tail fibres here begin to appear. 



A comparison of the two stages illustrates the gradual dwindling 

 of the cytoplasm which surrounds the bundle. It will be remem- 

 bered that shortly after the complete reconstruction of the spermatid 

 nucleus, cell boundaries disappear and the nuclei lie in a common 

 plasma. When, however, the nuclei come to be associated in 

 groups, the cytoplasm again becomes sharply defined and in cross 

 sections an appearance like that of separate cells is obtained (Fig. 

 80). The cytoplasm in the anterior region becomes comparatively 

 homogeneous and the nuclei often lie in a central clear space (Fig. 

 81^). More posteriorly it breaks up and assumes a granular 

 appearance (Fig. Zic), while still farther back the fibrillar bundles 

 lie isolated, with vague remnants of cytoplasm between them (Fig. 

 81). In Fig. 82 the diameter of the colony is less and the cyto- 

 plasm surrounding the fibres decidedly less extensive. 



The sperm colonies when mature, or nearly so, are forced into 

 the vas deferens, probably by contractions of the muscle layer of 

 the follicle. In the vas they are surrounded by a fluid secreted by 

 the large cells which form its lining, and which causes them readily 

 to adhere to needles or forceps. The mature colony has the appear- 

 ance shown in Figs. 85, Zd and 87. I have not heen able to isolate 

 a single colony entire, for in teasing the long fibres are almost 

 invariably torn. I have been able to trace them for a considerable 

 distance, however, and can state that they are exceedingly long. 

 The filamentous nuclei are invariably partially frayed from the 



