WENRICH: spermatogenesis of PHRYNOTETTIX MAGNUS. 81 



These variations may be due to one or more of several causes: — (1) 

 DiflFerenees arise on account of slightly different reactions to the 

 fixatives and stains. (2) There is a tendency for adjacent granules to 

 fuse, thus causing apparent variations in number and relative size. 

 (3) There is a slight difference in appearance at different stages. (4) 

 The different positions assumed by the element with reference to the 

 optical axis of the microscope may account for some variation in 

 appearance. (5) Some individual variation from animal to animal 

 might be expected. 



It will be noticed that the distal granule (no. 5) is single in all the 

 individuals except those represented at b and c, where it is double. 

 This is in accordance with the statement previously made (page 70) 

 that chromosome-pair B is unequal in eleven and equal in only two 

 of the thirteen animals studied. It will also be noticed that the 

 granules at the proximal end (no. 1) frequently become associated 

 with other polar granules in a composite granule (a, h, i, j, I, m, fig. 97), 

 and that with one exception (/) the distal end is free. The formation 

 of composite granules is a characteristic feature of this material, as 

 already noted on page 64. 



One of the granules of the proximal pair (no. 1) of individual /, 

 figure 97, is seen to be enlarged and less deeply stained than its mate. 

 Another example may be seen at k. I believe this to be an example of 

 a modification similar to that described in connection with the distal 

 granules of the pair A (p. 66). In B, this condition appears with 

 much less frequency, for in a count of 84 cases taken at random from 

 one individual only 14 (16|%) had one of the granules in the expanded 

 condition. This modification may persist into the tetrad stages, as 

 was the case with A. No case was found in which both granules were 

 expanded. 



In order to test the variability of the details of constitution of the 

 element 5 in a single animal, a study was undertaken with this object 

 in view. Sixteen drawings (fig. 98, a-p) were made of examples taken 

 at random from a single slide. Comparison shows about the same 

 degree of constancy in the composition of the elements here as in the 

 set from different animals. Some of the variations may be pointed 

 out. For example, the relative lengths of the segments 1-4 and 4-5 

 in example a, figure 98, are somewhat different from those in example 

 h. I think we may assume that the spireme threads possess some 

 elasticity and that the variation in arrangement, association, and posi- 

 tion of the several segments of the spireme may frequently bring about 

 stresses which may stretch some of the threads or parts of threads to a 



