The uterus has a muscular wall and a chitinous lining. Two repeatedly branched colleterial glands open into its under side. Of these the left is much the larger, and overlies the other. It consists of many dichotomous tubes, some of which are a little dilated at their blind ends. The gland is much entangled with fat-cells, which make it difficult to unravel. The right gland is probably of no functional importance; the left gland is filled with a milky substance, containing many crystals and a coagulable fluid, out of both of which the egg-capsule is formed.[164] [164] The crystals have been supposed to consist of oxalate of lime (Duchamp, Rev. des sci. nat. Montpellier, Tom. VIII.). Hallez observes that they are prismatic, with rhombic base, the angles truncated. They are insoluble in water and weak nitric acid, but dissolve rapidly in strong sulphuric acid without liberation of gas, and still more rapidly in caustic potash. (Compt. Rend., Aug., 1885.) At its hinder end the uterus opens by a median vertical slit, which lies in the 8th sternum, into a genital pouch which represents part of the external integument, folded back far into the interior of the abdomen. (See fig. 96.) Upon the dorsal wall of the genital pouch the orifice of the spermatheca is situated.[165] This is a short tube dilated at the end, and wound into a spiral of about one turn. From the tube a cæcal process is given off, which may correspond with the accessory gland attached to the duct of the spermatheca in many Insects (_e.g._, Coleoptera, Hymenoptera, and some Lepidoptera). The spermatheca is filled during copulation, and is always found to contain spermatozoa in the fertile female.[166] The spermatozoa are no doubt passed into the genital pouch from time to time, and there fertilise the eggs descending from the ovarian tubes. [165] It is usually stated that the spermatheca of the Cockroach opens into the uterus, as it does in most other Insects, but this is not true. Locusts and Grasshoppers have the outlet of the spermatheca placed as in the Cockroach; in other European Orthoptera, it lies upon the dorsal wall of the uterus. (Berlese, loc. cit., p. 273.) [166] It is a striking proof of the sagacity of Malpighi, that he should have observed in the Silkworm the spermatophore of the male (“in spiram circumvolutum persimile semen”) and the spermatheca of the female. His reasoning as to the function of the spermatheca wanted nothing but microscopic evidence of the actual transference of spermatozoa to establish it in all points. Audouin and Siebold supplied what was wanting nearly two centuries later, but they mistook the spirally wound spermatophore for a broken-off penis, and Stein (Weibl. Geschlechtsorgane der Käfer, p. 85) first arrived at the complete proof of Malpighi’s explanation.