CHROMOSOMES OF TIGER BEETLES 459 
more conspicuous, definite granular threads radiate from these 
ehromatin masses (figs. 95 and 96). As the number and prom- 
inence of these chromatin threads increase, there is a corre- 
sponding decrease in the chromatic masses (figs. 96 and 97). 
This observation indicates that each leptotene thread is derived 
directly from an oogonial chromatic mass. This seems espe- 
cially conclusive since the estimated number of leptotene threads 
approximate the number of oogonial chromosomes. In the typ- 
ical leptotene nuclei (figs. 97 and 98) the long threads are twisted 
and irregularly arranged throughout the nucleus. They are 
usually attached to the nuclear membrane at one or both ends 
.by an accumulated mass of chromatin-staining material. A 
cross-section not only shows a number of cut ends, but threads 
at various foci, depending upon the loop of the threads and angle 
of the section. It will be noted that these threads are rendered 
much more conspicuous by the granular enlargements—the 
“chromomeres. 
B. Sex chromosomes 
The telophase of the last oogonial division shows all the chro- 
matin masses of about the same density. However, in very 
early growth period, only one or two condensed bodies remain, 
and these show little relation to the chromatin fibers. This 
becomes especially apparent a little later when all other chro- 
matin bodies have been transformed into the leptotene threads. 
In the earlier stages these bodies are usually compact (figs. 95, 
96, and 97), but in later growth period they appear irregular 
and woolly (fig. 105). 
Although the evidence is not conclusive that these bodies are 
the sex-chromosomes, it seems reasonable to assume that such 
is the case. According to the observational evidence illustrated 
in the fertilization formula, the cells of the female should con- 
tain twice the amount of X-chromatin as those of the male. 
That is, the male possesses X + x, while in the female cell there 
should be found 2X + 2x. In accordance with these conclu- 
sions, observations further indicate that the chromain content 
of the chromatin nucleolus of the female will approximate twice 
