1912.] The Anatomy of a Slug. 195 
(2) The albumen gland is an elongated body with the posterior 
end flattened and attached to the ovary. The anterior end is 
narrow. ‘The upper convex surface of the gland is smooth, but 
present numerous transverse fissures. It is indented with a 
longitudinal groove for the intestine. The inner surface is concave 
and presents a depression for the penial sheath over which it lies. 
Minute structure (pl. xxvii, fig. 29).—The gland is composed of a 
number of lobules bound together loosely by connective tissue. Each 
lobule is formed by a group of tubular acini, each of which seems 
to end in a duct which unites with others to forma main duct 
opening into the oviduct. Each acinus is enclosed by a basement 
membrane. Inside it is the epithelium consisting of a single 
layer of polyhedral cells with large round nuclei placed towards 
the base. The inner free borders of the cells are broken and 
jagged. The inner two-thirds of the cells are filled with coarse 
granules. The cavities of the acini are filled with the secreted 
material which is stained deep blue with hematoxylin. The 
ducts of the acini are lined with columnar epithelium. 
(3) The oviduct is a thin-walled tube passing through the 
substance of the albumen gland and emerges through its anterior 
extremity to end in the vagina. 
Minute structure (pl. xxvii, figs. 30, 31).—The wall consists of 
a thin outer layer of connective tissue which is continued into the 
centre of the longitudinal folds projecting into the lumen. 
Inside this layer is a coat of connective tissue cells with a few 
fibres between them. These are also continued into the folds 
and surround the central strands of connective tissue. The 
mucous membrane consists of a single layer of ciliated columnar 
epithelium. 
(4) The vagina is a stout tubular structure slightly curved 
with the convexity downward and to the right. The upper 
surface presents a groove for the intestine. 
(5) The receptaculum seminis is an oval body with a fairly 
long tubular stalk opening into the middle of the vagina on its 
side. : 
(6) The female genital aperture in which the vagina ends, 
lies in the groove between the foot and right mantle border 
at a distance from the anterior end of the body already noted 
in a tabular form. 
VII. NERVOUS SYSTEM (pl. xxvii, fig. 32). 
The nervous system is of euthyneurous type. The ganglia 
are closely united to form a mass round the oesophagus. The 
cerebral ganglia are closely connected to each other by a short 
thick intercerebral commissure. ‘The cerebro-pedal and cerebro- 
pleural connectives are united to form a short thick band on 
each side. The buccal ganglia are placed on the ventro-lateral 
aspect of the hinder end of the proboscis-sheath at the junction 
with the radulasac. The stomato-gastric connectives are long 
