444 j. bkonte , gatenby. 
than that of the male, though this may be accounted for 
when one remembers " that the fixing fluid has different 
amounts of tissue to penetrate in the testis than in the ovary, 
and length of fixation and accessibility to fixation will cause 
great differences in staining. 
I liave been unable through Jack of suitable material to 
follow the micromitosome through oogonial divisions, but it 
is quite possible that the nurse-cells differ from the oocytes 
in that the latter may possess a micromitosome, the former 
not. The search I was able to make showed that this view 
may be true, but good enough mitoses were not available 
to follow this body. It is very plain in Pygsera 
bucephala, and this moth will make a good species for 
study, because its cells are so large. In later oocytes 
(PI. 24, fig. 29) one often finds a large vacuolated body 
marked X. which I believe is the micromitosome; it seems 
to break up about this period ; but my material is not 
extensive enough to allow me to make a definite state- 
ment. 
In PI. 24, figs. 25, 26, and 28, the centrosome and 
mitochondria are shown. The latter are somewhat different 
from those of the male ; this difference may be due to the 
accessibility to the fixative in the female, for in later stages I 
know that the more peripheral spermatocytes and spermatids 
are differently fixed from the medullary ones. In the male 
the mitochondria are granular, in the female fibrous, but 
exactly this difference in later stages can be demonstrated 
in the male. (Compare PI. 25, figs. 30 and 31.) The 
mitochondria of the female never become far removed from 
the nucleus, are always minute, never have formed within 
them the cliromopliobe medulla, and in late stages form a 
cap on one side of the nucleus (PI. 24, fig. 29). Their 
subsequent fate in the maturation divisions and in fertilisa- 
tion is unknown. 
It is noticeable that the semilunar cloud of granules near 
the oocyte nucleus is not destroyed by acetic acid fixatives 
-at this period, and in this way resembles the mitochondrial 
