WENRICH: spermatogenesis of PHRYNOTETTIX MAGNUS. 89 



vesicular membranes between adjacent vesicles within the group, 

 especially at the polar end, (4) the formation of an irregular nuclear 

 membrane from the outer walls of the vesicles, (5) the apparent 

 anastomosing of the edges of the networks arising from the diffusion 

 of the chromosomes in adjacent vesicles. The walls bounding the 

 original vesicles are still to be seen in figures 8-13, and this is particu- 

 larly true of the accessory chromosome, the vesicle of which persists 

 till a late prophase. 



What can we now say as to the continuity of the individual chromo- 

 somes? Let us first follow the changes undergone by the accessory 

 chromosome. Figures 1 and 2 are of metaphases, in which all the 

 chromosomes except the accessory are compact and smooth in outline. 

 This is roughened in outline and seems to have already begun the 

 process of expansion which characterizes its behavior immediately 

 after division. In figure 4 a hyaline area of considerable extent has 

 already been formed about the accessory, and close examination 

 reveals also a narrow hyaline area just beginning to develop around 

 each of the autosomes. By the time the stage shown in figure 6 is 

 reached, the substance of the accessory has become distributed through 

 the entire space of the vesicle which accompanied the formation of the 

 hyaline area. In its distribution within the vesicle, the chromatic 

 substance is more concentrated on the periphery of the sac, than 

 through the central space. The vesicle continues to expand along 

 with the expansion of the nuclear material as a whole, until the stage 

 of greatest diffusion of the autosomes has been reached (fig. 12 and 13). 

 At the stage shown in figures 14a and 14b (Plate 2) the chromatin has 

 begun to concentrate towards the axes of the sacs, but this process 

 seems to be less advanced in the accessory {X, fig. 14b) than in the 

 autosomes. These are the earliest of the prophases. In the later 

 prophases, as shown in figures 17 and 20, the accessory becomes 

 concentrated as a coiled thread running down through the middle of 

 the vesicular space. The wall of the vesicle persists longer than does 

 that of the nucleus as a whole or that of the other autosomes (fig. 20). 

 There can be no question, it seems to me, that the accessory main- 

 tains a persistent individuality through all these stages. 



If now the changes undergone by the autosomes be followed, we 

 shall find for them also evidences of persistent individuality. I think 

 no one would deny a persistent individuality up to the stages shown in 

 figures 8 and 9 (Plate 1) . In these figures the chromatin has become 

 reticular, but the masses representing individual cliromosomes are 

 still quite distinct and surrounded for the most part by the persisting 



