WENRICH: SPERMATOGENESIS OF PHRYNOTETTIX MAGNUS. 67 
Stage Total Expanded Not expanded % Expanded 
Spireme fii 94 7 93 .06 
Postspireme 162 146 16 90.12 
Both stages 273 240 23 91.26 
It will be seen from this table that approximately 90% (examples 
counted at random) have one of the granules in the expanded condi- 
tion. In the postspireme stages this peculiarity appears less like an 
expanded single granule than as a group of closely associated small 
granules, typically three in number. This condition will be discussed 
more fully in another place (p. 112). In both the spireme and the 
postspireme stages the modified polar granule furnishes a ready means 
of identification of chromosome-pair A, especially when its staining 
qualities, already described, are taken into consideration. The con- 
stant relative size of A in the tetrad stages is also a help in identifica- 
tion. . 
Figure 62 (Plate 6) indicates clearly the processes by which the 
spireme loop becomes first transformed into a typical tetrad, and then 
condensed to a metaphase chromosome. From the zygotene stage 
onward, there is a gradual shortening of the spireme loops or segments. 
The later stages of this process are to be seen in figure 62. Through- 
out the pachytene stage the spireme loops exhibit a median longi- 
tudinal cleft, usually referred to as the longitudinal split. I shall call 
this the primary longitudinal split. Occasionally paired granules, or 
chromomeres, appear to be fused together, but as a general rule, the 
split is continuous throughout the length of the loop. In my opinion 
this so-called longitudinal split is really the space between two spireme 
(leptotene) threads which have conjugated side-by-side. Further evi- 
dence for this belief will be presented later. 
Figure 62, c, indicates the first step in the process of forming the 
four chromatids of the tetrad. A second longitudinal split, at right 
angles to the first or primary split, begins at the proximal end (upper 
end in the figures) of the free spireme segment (fig. 62, c) and gradually 
proceeds toward the distal (lower) end (fig. 62, c-e). It will be seen 
from these figures that as the separation produced by the secondary 
split proceeds distally, the separated chromatids at the same time 
reunite along the plane of the primary split. The separation due to 
the secondary split gradually increases until the diverging pairs of 
chromatids extend in opposite directions, thus forming a rod-like 
element the two ends of which correspond to the proximal pole of the 
