SEX DETERMINATION IN DfNOPHILUS GYROC1LIATUS. 369 
tinguishable witli male and female pronucleus. Fixed sublimate- 
acetic. 
Fig. 22. — Mass of yolk material from ovary, formed as the result 
of the fusion of a number of oogonial cells. Their nuclei are shown 
around the periphery of the mass undergoing active division. Male 
and female portions of these nucleoli clearly distinguishable. Sublimate- 
acetic. 
Fig. 23. — Fully formed female egg from ovary, in which the two 
portions of the nucleus, male and female, can still be distinguished. 
Sublimate-acetic. 
Fig. 24. — Aceto-carmine preparation of a portion of the ovary of 
young female, somewhat older than in the stage shown in fig. 20. The 
primitive oogonia are somewhat larger, and the sperm that are attached 
to them are losing their tails. 
Fig. 25. — Section through the ovarian region of a young female, just 
after leaving the egg-capsule. No trace of the female germ-cells can 
be distinguished, and only the mass of sperm which the female has 
received from the male before leaving the egg-capsule is distinguishable. 
Fig. 26. — Ovarian male egg usually much more granular than the 
female egg and with only usually one nucleolus. Sublimate-nitric. 
PLATE 32. 
Fig. 27.— Immature partially formed female egg showing two portions 
of nucleus. Sublimate-acetic. 
Fig. 28. — Yolk mass from ovary showing two nuclei, each showing 
male and female chromatic bodies. Sublimate-nitric. 
Fig. 29. — Nucleus of female ovarian egg. showing its division into 
male and female portion. Sublimate-acetic. 
Fig. 30. — Mitotic figures in first segmentation division of female egg. 
Stained Lithium carmine and Lyons blue. 
Fig. 31.— Ovarian egg formation, showing division of two cells, 
in one of which male and female portions of the nucleus have 
divided equally, while in the other the male portion has gone wholly 
over to one side. Sublimate-nitric. 
Fig. 32.— Section through the ovarian region of a ripe female, similar 
to fig. 21, showing the eggs crowded together. Fixed in sublimate- 
nitric. 
Fig. 33. — Section of ovarian eggs similar to fig. 31. Showing in one 
cell the male and female portions of the nucleus equally divided, while 
the other shows the male nucleus only on one side. Sublimate-nitric. 
