INTERNAL GENERATIVE ORGANS OF THE FEMALE. 677 
The Genital Fosse.—These remarkable depressions in the 
dorsal wall of the uterus are probably concerned in the act of 
copulation. They are fully developed in the female when it 
emerges from the pupa, and are protected by a thick laminated 
cuticle. They probably lodge the curved spines of the penis 
during copulation. Although the distance of this fossa from 
the vulva is very considerable in the adult female when the 
ovipositor is exserted, in the young female it lies close to the 
vulva. The ovipositor is closed up by its joints being with- 
drawn one within the other, like the tubes of a portable tele- 
scope, and the vagina is also invaginated in four folds, one within 
the other, so that the bursa, as the young uterus is termed, 
opens directly through a very short segment of the vagina by 
the vulva. 
The Receptacula Seminis.—These organs serve as a receptacle 
for the sperm of the male; for although Insects have the 
sexes distinct, the sperm is transferred from the male by a 
single sexual act to the bursa, or to the receptacula seminis of 
the female, where it remains for days, months, or even for 
years before the ova are fertilised. Fertilisation is effected as 
the ovum passes through the oviduct, so that the actual act of 
fertilisation is not effected by the union of the sexes. 
In the Lepidoptera, the bursa does not communicate directly 
with the oviduct, and opens externally by an orifice on the 
ventral surface of the abdomen, in front of the orifice of the 
oviduct. The sperm is afterwards conveyed into the oviduct 
by the spermatic canal, which unites the two cavities. 
In most insects the sperm is preserved in the spermatic 
capsules, or receptacula seminis. In the Diptera these are 
always three in number, two on one side, and one on the 
other. 
In the Blow-fly the receptacula seminis, or spermathece, 
are small capsules, which have a long diameter of ‘2 mm., and 
a short diameter of about ‘125 mm. There are two on the 
right side, and one on the left, connected with the uterus by 
long muscular ducts, one to each capsule. The orifices of 
these ducts are close together, immediately in front of the 
