WENRICH: spermatogenesis of PHRYNOTETTIX MAGNUS. 85 



would enable one to trace them, as was done in the case of chromo- 

 some-pair A. It is a matter of no small importance, I believe, that 

 each of the "selected" chromosome-pairs has been recognizable by 

 means of one or both its members, in the spermatogonia as well as in 

 the spermatocytes. 



On the other hand, when I came to search through the postspireme 

 stages of the other individuals for tetrad C, I was able to find the 

 condition shown in figure 65 in only two instances; but a careful study 

 of these stages in the rejnaining animals of the series revealed, in 

 place of the large unequal type shown in figure 65, two other types, 

 which are shown in figure 107, c~m. Figure 106 presents an example of 

 tetrad B from each of the thirteen animals from which material was 

 available for study, and figure 107 a similar series of tetrad C. The 

 corresponding letters, a, h, c, etc., in the two series represent the same 

 animal. We may therefore, speak of the different animals as a, b, c, 

 etc. Cliromosome-pairs B and C are the smallest in the whole com- 

 plex and it will be seen from these two series of drawings that, except 

 in a and b, the pair C is the smaller of the two. In a and b, C is slightly 

 larger than B, as was determined by numerous comparisons in the 

 metaphases of the first spermatocytes. The difference in quantity of 

 chromatin in these two cases is quite small, however, and differences 

 in shape and 'behavior were largely depended on for identification. 



For convenience in description, we may designate the three types 

 of chromosome-pair C as Ci, C2, and C3. By Ci will be indicated 

 the type, previously described, which is represented in figure 65, and 

 at a and b in figure 107. The type shown in figure 107, c-h, may be 

 designated Co, and that shown in figure 107 at i-vi, as C3. Thus it 

 will be seen that (with a possible exception yet to be discussed) of the 

 thirteen animals studied, two exhibited the type Ci, six the type C2, 

 and the remainder, five, the type C3. 



If now we compare types Ci and C2, it will be apparent at once that 

 both members of the pair C2 resemble the smaller member of Ci. 

 The homology is striking if one notices the polar granules and the pair 

 of granules close to them, both of which appear in about the same 

 relative size and position in all the examples of both types (except h). 

 It is therefore not difficult to believe that type Co does actually repre- 

 sent a pair of chromosomes homologous to the smaller conjugant in 

 type Ci. 



Turning to type C3, as shown in figure 107, i-m, it will be observed 

 that this is quite different from either Ci or C2. It represents an 

 unequal pair but the larger member is very different from the larger 



