with a duct for the conveyance of the eggs to the exterior, and the arrangements of the tubes with regard to the oviduct also vary much. An interesting condition is found in _Machilis_ (see Fig. 94, p. 188), where the seven egg-tubes are not arranged in a bunch, but open at a distance from one another into the elongated duct. The two oviducts usually unite into one chamber, called the azygos portion or the uterus, near their termination. There are a few Insects (Ephemeridae) in which the two oviducts do not unite, but have a pair of orifices at the extremity of the body. Hatchett-Jackson has recently shown[64] that in _Vanessa io_ of the Order Lepidoptera, the paired larval oviducts are solid, and are fixed ventrally so as to represent an Ephemeridean stage; that the azygos system of ducts and appended structures develop separately from the original oviducts, and that they pass through stages represented in other Orders of Insects to the stage peculiar to the Lepidoptera. _Machilis_, according to Oudemans, is a complete connecting link between the Insects with single and those with paired orifices. There are in different Insects more than one kind of diverticula and accessory glands in connexion with the oviducts or uterus; a receptaculum seminis, also called spermatheca, is common. In the Lepidoptera there is added a remarkable structure, the bursa copulatrix, which is a pouch connected by a tubular isthmus with the common portion of the oviduct, but having at the same time a separate external orifice, so that there are two sexual orifices, the opening of the bursa copulatrix being the lower or more anterior. The organ called by Dufour in his various contributions _glande sébifique_, is now considered to be, in some cases at any rate, a spermatheca. The special functions of the accessory glands are still very obscure. [Illustration: FIG. 75.—Egg-tube of _Dytiscus marginalis_; _e.c_, egg-chamber; _n.c_, nutriment chamber; _t.c_, terminal chamber; _t.t_, terminal thread. (After Korschelt.)]