430 PROF. B. T. LOWNE ON THE STRUCTURE AND 
itself, it belongs entirely to tbe ovum, and cannot be regarded as 
the epithelium of the ovarian follicle, which is quite distinct and 
remains in the follicle. 
I am also inclined to regard the vitelline membrane as tbe 
cuticular exudation from the inner surface of the epithelium of 
the ovum and the chorion as the modified epithelium itself. The 
cuticular sheath which leaves the ovarian follicle with the egg 
is, I have little doubt, the epichorionic membrane described by 
Leuckart, Robin, and Kolliker. The shedding of the outermost 
covering of the egg, probably the epichorionic membrane, and 
possibly also of the epithelial chorion, was observed by Brandt 
in the Field-crickets in transit through the oviduct, forming 
what he designates corpora lutea. 
The micropyle-canal, which, in the Diptera, extends the whole 
length of the dorsal surface of the egg, is an infoldiug of the 
chorion (PI. XXVIII. fig. 9). It is extended over the anterior 
egg-pole (fig. 10), forming a considerable chamber in the floor 
of which the micropvle is situated (fig. 10, m). 
The micropyle (figs. 12 & 13) is a small, almost quadrilateral 
opening (fig. 12), 2 5 g in diameter ; it is surrounded by a 
number of radiating folds which project on the outer surface of 
the chorion, and by a circular area composed of small hexagonal 
cells. These correspond in size to the hexagonal fields with 
which the rest of the chorion is sculptured. 
The open micropyle-canal is brought into relation first with 
the orifices of the gum-glauds, and later with those of the 
spermatophorous capsules during the descent of the egg through 
the genital canal. Ilenkiug (9) found spermatic filaments in the 
micropyle-canal. 
3. The Oviducts and their Appendages. 
The general form and arrangement of these parts is well 
known, so that tbe following description will suffice to indicate 
their arrangement for my present purpose. 
The ovarian ducts are two in number (fig. 2), and these form 
a common oviduct ( od ) by their union. The common oviduct 
opens into the pouch-like anterior extremity of the vagina on its 
dorsal aspect. 
