404 
Tetrarliyncims erinaceus 
also becomes very irregular and finally disappears so that the wall of the 
oviduct comes to consist only of the intermediate basement membrane. 
One is forced to regard this as the definitive wall of the duct, and the 
outer and inner layers of cells or nuclei as the formative organs of this 
structureless membrane. The canalis seminalis from the receptaculum 
seminis opens into the proximal part of the oviduct while it is still run¬ 
ning posteriorly, and immediately afterwards the vitelline duct also so 
debouches. The oviduct now turns forwards, receiving as it does so the 
efferent stalks of the cells composing the shell gland. 
The shell gland. (PI. XX, fig. 10; PI. XXIII, fig. 25.) This consists 
of a great number of flask-shaped cells arranged round the bend of the 
oviduct in the form of a hemispherical shell, the concavity of the 
shell being directed anteriorly. The cells radiate inwards towards 
the oviduct and join the latter near the place where the canalis 
seminalis and vitelline ducts open. Each cell, which is about 0'03 mm. 
in greatest length, is a unicellular gland, and contains a large nucleus 
in which there is a nucleolus with refringent granules. The distal part 
of the cell, which is bulb-shaped and contains the nucleus, stains light 
red with methyl-blue-eosin, but the proximal part is stalk-shaped and 
stains deep blue. The stalk runs towards the oviduct and then frays 
out into a number of delicate filaments which penetrate between the 
layer of cells, or nuclei, forming- the outer portion of the wall of the 
former. At tins part of the oviduct the basement membrane disappears 
and the filaments can be traced between the cells forming the internal 
layer, and can sometimes be seen even in the lumen of the duct. But 
it is probably the secretion of the cells which one sees here, for both the 
lumen of the duct and the interstices of its wall may exhibit the blue 
staining reaction characteristic of the secreting part of the shell gland 
cells. 
The uterine canal. (Pis. XXI and XXIV.) We can recognise three 
regions in the female genital tract: (1) from the ovary to the junction 
of the canalis seminalis; (2) from the latter point to the opening of the 
vitelline duct; and (3) the remainder of the canal. Two views may be 
held with regard to the nature of the whole canal; (1) that it is the 
continuation of the vagina, and that both oviduct and vitelline duct 
open into it; (2) that it is everywhere morphologically a true oviduct 
which receives the canalis seminalis and vitelline ducts. However this 
may be it is evident that the canal beyond the place of entrance of the 
other ducts is different from the more proximal tract in that it contains 
eggs which are fertilised and yolked,and it has therefoi'e been called by 
