Spermatogenesis in spiders. 515 



logical basis for the dimorphism. Six specimens of the gray variety 

 and five specimens of the tufted males were sectioned and studied. 



Spermatogenesis of Gray variety of Maevia vittata. 



Spermatogonia! prophase. If an immature male is 

 sectioned the testis will usually be found crowded with spermato- 

 gonia! cells which have the form shown in Fig. 1. It is difficult 

 to make out the boundaries of the individual cells but the nucleus 

 of each is quite distinct, and we find lying within it chromatin 

 bodies which appear to be connected by fine linin threads. These 

 chromatin masses lie at different levels in the nuclear cavity; there 

 is little variation in the size of the individual knots and for the 

 most part the outlines are regular. Repeated counts show that 

 these bodies are present in approximately the same number as the 

 spermatogonia! chromosomes and they probably represent the latter 

 at this time. 



If we section a mature male we find a few of the spermato- 

 gonia! cells just described, lying on the periphery of the testis and 

 here and there will be a dividing spermatogonia! cell. The latter 

 are comparatively rare, although, in a number of cases, cysts were 

 found in which all phases of the last spermatogonia! division and 

 the very early primary spermatocytes were present. 



This prophase stage, shown in Fig. 1, is a very definite and 

 characteristic period not only for Maevia but for many other spiders 

 as well. It persists for a considerable time and we have here, 

 apparently, a very simple explanation for the way in which the 

 sperm of spiders may all become fully formed at about the same 

 period. ^). 



Following the prophase stage we have the formation of the 

 spermatogonia! chromosomes. The way in which these chromosomes 

 arise from the knots of the prophase period is not clear but it seems 

 to be by a process of swelling or growth of the latter bodies. The 



1) In the males of most spiders, the maturation divisions of the germ 

 cells are passed through immediately after the last moult, when they bear 

 the fully formed palpi. The development of the sperm is thus not 

 continuous but seems to take place in a very short period of time. The 

 primitive forms are exceptions to this. Apparently, the spermatogonia! 

 cells reach the prophase stage just described and remain unchanged until 

 the stimulus for further development comes. Then they pass through the 

 divisions vv^ith great rapidity. 



