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Show 674 VISCERAL ANATOMY OF THE AUSTRALIAN TORPEDO. [Dec. 2, similarity to that of the ventral mesentery of some Teleostei (ex. Salmo) to venous trunks which pass between the intestinal and ventral body walls *. O n the whole, and on consideration of the facts referred to in dealing with the Anurous Amphibia, I a m disposed to regard the disposition of the great vessels named as the primary agent in originating the absorption under consideration. The so-called abdominal pores of the cartilaginous fishes have been shown by Bridge2 to arise in relation either to peritoneal pouches (dv.p., fig. 5) resulting from outward extension of the peritoneum, or to cloacal pits (dv.c.) formed by inward extension of the ventral body-wall. In the specimen of Hypnos here figured, the two were in wide communication on the left side, sufficient to pass a crow-quill; on the right side the base of the peritoneal pouch (cf. fig.) was constricted, whereby it communicated with the cloacal pit by a minute aperture in its "dorsal wall. This is of interest, as Bridge's researches have shown the parts in question to be variable specifically and individually to an unexpected degree. DESCEIPTION O F P L A T E LVII. Fig. 1. Hypnos subnigrum, $. General disposition of the viscera, as seen on reflecting the ventral post-pericardiac body-wall. One third nat. size. 2. The same. The alimentary viscera, dorsal mesentery, and testis, as seen from the right side. One third nat. size. 3. The same. The spleen and appendix digitiformis, represented in relation to the dorsal mesentery (indicated by a black line a, (3). Two thirds nat. size. 4. The same. The Bursa Entiana, together with the head of the small (valve-bearing) intestine and the pyloric chamber of the stomach ; laid open from the left side, to show their contained valves. Two thirds nat. size. 5. The same. Peritoneal pouch and cloacal pit of the right side, lateral view from within. Nat. size. Reference letters. a.m'. Anterior superior mesenteric artery. a.m". Posterior superior mesenteric artery. ap. Appendix digitiformis. cd. Stomach (cardiac sac). c.b. Gall-cyst. cl. Cloaca. d.h. Bile-duct. d.m. Miillerian ducts (coalesced ostia of). dv.c. Cloacal pit. dv.p. Peritoneal pouch. f.m. Mesenteric furrow. f.p. Gastric furrow. hp. Liver. ' Cf. Stannius, op. cit. pp. 250, 251. 2 Journ. Anat. & Phys. vol. xiv. p. 81 (1879). |