. Elementary text-book of zoology. Zoology. 64 MOLLUSCA. fis (k abdomen. They open into the mantle cavity, each through the apex of a papilla. The anterior walls of the sacs are pushed inwards by csecal appendages of the vense cav* (branchial arteries), so as to give rise to a number of racemose lobules projecting into each renal sac (fig. 536). The renal sacs, as in other Molluscs, communicate with the body cavity, which in Sepia is largely developed and contains the heart, generative organs, etc., but in the Octopoda is reduced to a narrow tubular space (" water - vascular sys- tem &quo
. Elementary text-book of zoology. Zoology. 64 MOLLUSCA. fis (k abdomen. They open into the mantle cavity, each through the apex of a papilla. The anterior walls of the sacs are pushed inwards by csecal appendages of the vense cav* (branchial arteries), so as to give rise to a number of racemose lobules projecting into each renal sac (fig. 536). The renal sacs, as in other Molluscs, communicate with the body cavity, which in Sepia is largely developed and contains the heart, generative organs, etc., but in the Octopoda is reduced to a narrow tubular space (" water - vascular sys- tem " of Krohn) and only contains the sexual glands. An excretory organ very generally present is the ink-sac. It is a piriform sac, whose duct opens to the exterior with the anus, and empties an intensely black fluid, which sur- rounds the body of the animal as in a black cloud, and so protects it from the pursuit of larger marine animals. The Cephalopoda are dioecious. Males and females present external sexual differences which principally concern a particular arm. Accord-. FIG. 537.—Anatomy of the body of a female Sepia (after C. Grobben). Ov, ovary in its cavity (body cavity) which is laid open; Od, oviduct; Oe, opening of the same; OdD, oviducal gland ; Nd, nidamental gland ; AD, accessory nidamental gland ; JV, kidney ; U, ureter; Lk, canal of the body cavity (water canal); Kh, branchial heart; Kha, pericardia! gland (appendage of branchial heart); K, gills; Af, anus ; tfst, stellate ganglion. ing to the discovery of Steenstrup, one of the arms in the male always becomes modified, hectocotylized as it is called, as an intromittent organ. The two sexes of Argonauta differ considerably, inasmuch as the small male has no shell. The sexual glands lie freely in the body cavity. Their products are dehisced into the body cavity, from which they are taken up and conveyed to the exterior by special ducts. The ovary is unpaired and racemose, and the oviduct is a double (Octopoda) or
Size: 1359px × 1839px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
