OCR Text |
Show 1880.] THE GENUS GIRASIA. 297 of the shorter portion (Plate XXVI. fig. 3, a) to the aperture within the vagina and ovo-testis (Plate X X V I . fig. 4, j. sp.). Macrochlamys decussata, of which I have a drawing, taken when the animals were in coitu, protruded a large white bladder-like sac, which expanded and contracted from time to time as if inflated with air ; this I now think may have been the spermatheca drawn out and receiving the penis and capreolus. In the two specimens I examined, the spermatheca (sp.) was elongate, smooth, lying close to and partly enveloped by the convolutions of the oviduct & c , with its posterior end near the junction of the hermaphrodite duct and albumen-gland. This posterior termination is bent over on itself, presenting a smooth rounded end (Plate X X V . figs. 2 & 4), which, coiling round, terminated, and was covered with what was apparently muscular tissue buried in the prostate and oviduct. The form of the spermatheca is due to its contents; and the rounded end is produced by the bending-over of the flagellum-like terminations of the enclosed spermatophores. In one specimen of G. hookeri which I examined, probably taken in the cold weather, all the generative organs are small and contracted, the spermatheca only represented by an attenuate sac. The amatorial organ or dart-sac (D)1 is a long cylindrical body narrowing towards the genital aperture, and again swelling there into a large orifice; it has a very thick and muscular structure, and in these spirit-specimens is very hard and unyielding. When cut open longitudinally, the dart or spiculum amoris was found to be a simple cylindrical rod, sharply pointed (Plate X X V I . fig. 7). This organ has a strong retractor muscle, with its attachment near that of the penis. Relative Position of the different Parts in G. gigas.-On cutting through the skin of the upper side of the back, commencing from between the eye-tentacles, the penis is seen lying in the middle line between the inverted eye-tentacles (Plate X X V . fig. 2) ; on the proper left of it are seen three large convolutions of the intestine (i); and on laying it over to the right side the salivary glands of flattened form are seen spreading over these, and a distinct connexion with the central convolution was very clearly made out (fig. 5, a). Proceeding; from the sides of the buccal mass will be noticed two strong; muscles, which have their attachment on the frontal margin of the body-cavity, at the point (Plate XXIV. fig. 3) m; these are the retractor muscles of the head and buccal mass. The spermatheca lies on the right side of the animal, covered partly by the oviduct; and a large expansion of the intestine occupies the posterior portion of the cavity, narrowing suddenly to enter that of the shell above. A very large mucous gland lies next the sole of the foot along the whole length of the body-cavity ; and two large pedal nerves are conspicuous and traverse it, throwing off nerves to the epidermis, and extend onto the caudal gland. 1 Glandula mucosa cum sagitta amatoria. |