756 THOS. H. MONTGOMERY, JR. 
considering the autosomes. The smaller idiochromosome is 
marked by the letter d in the early spermatocytes of figs. 5 to 9, 
here distinguishable by its size alone. In the cyst from which fig. 
9 was made several nuclei exhibited this element in the form of 
a small rod, as there shown. As the autosomes become less 
compact and with Hermann’s triple stain change from red to 
violet in their color, the idicchromosomes become distinguishable 
by remaining more dense and continuing safraninophilous. ‘Thus 
in figs. 13, 15, 18-20 an idiochromosome is readily discernible, 
but whether this single one is the large idiochromosome, the smaller 
in that case being hidden, or whether this is the smaller, could not 
be told with certainty. But from the stage of fig. 22 on, both of 
them can be recognized whenever the whole nucleus lies within 
the section. From these stages until the late prophases following 
they continue in contact with the nuclear membrane, but maintain 
no particular location upon its surface. They are at first sepa- 
rated from each other (figs. 22, 23, 27), but later come together 
(figs. 26, 28-30, 33, 34, 36-40, 42, 44, 48-56). But there is either 
variation in the time of their conjugation, or else it may be that 
after an initial conjugation they may undergo a temporary separa- 
tion; thus they are seen separated in figs. 41, 46, 47. At first 
they are rather irregular in form (figs. 22, 23,25, 26), then become 
more or less straightened (figs. 28-30, 36, 38, 39, 42); perhaps 
they are not so variable in form as the optical appearances suggest, 
for the supposed variation may be due in part to the angle of 
vision. Occasionally one or both may seem bilobed, perhaps 
an indication of a process of longitudinal splitting (figs. 42, 44— 
46, 48, 50, 51, 55; see also fig. 6 of my paper of 701). Each rounds 
up later and develops a clear vacuole within its interior (fig. 58). 
At the same time the two that had been rather loosely apposed 
become compacted together, so that from the stage of fig. 57 on 
until the late prophases a bivalent idicchromosome (Dd) is found 
in most nuclei (figs. 59-68, 69, 70). The bivalent idiochromosome 
sometimes exhibits two vacuoles (fig. 59) which evidently corre- 
spond to the two of the separated idiochromosomes of fig. 58, but 
more usually contains a single vacuole; this larger vacuole is 
then probably a fusion of the two single ones accompanying the 
