Online Encyclopedia

CEPHALOPODA

Online Encyclopedia
Originally appearing in Volume V07, Page 675 of the 1911 Encyclopedia Britannica.
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CEPHALOPODA. In the family Cheiroteuthidae many of the species occur at abyssal depths of the ocean, and exhibit curious modifications of structure. In Cheiroteuthis itself the tentacular arms are very long and slender, and are not capable of retraction into pockets. In several species of this genus the suckers are no longer organs of adhesion, but are simple cups containing a network of filaments resembling a fishing net. In Histioteuthis and Histiopsis, as in some Octopods, the six dorsal arms are more or less completely united by a web, which also probably serves for capturing fish. In these two genera and in Calliteuthis the skin bears luminous organs. Cheiroteuthis has been taken at 2600 fms., Calliteuthis at 2200, Histiopsis at nearly 2000. Bathyteuthis, placed in the same family as Ommatostrephes, has been taken at 1700 fms. The Cranchiidae are remarkable for their small size, the shortness of the ordinary arms, and the protuberance of the eyes, which in Taonius are actually on the ends of stalk-like outgrowths of the body. Cranchia is a deep-sea form taken at 1700 fms. Its body is pear-shaped, swollen posteriorly and quite narrow at the neck. Spirula is distinguished from all other existing Cephalopods by the structure of its coiled shell, which in many respects resembles those of the extinct Ammonites, and is not completely internal. In the structure of the body the animal is a true cuttlefish in the sense in which the term is here used, having ten arms and a perforated cornea. Three species are distinguished, and their empty shells occur abundantly on the shores of the tropical regions of the Atlantic, Pacific and Indian Oceans. In German the shells are known from their shape as Posthornchen. They are common on the shores of the Azores. But the animal has very rarely been obtained; only a few specimens occur in museum collections. One specimen was taken by the " Challenger " in a deep-sea trawl, at a depth between 300 and 400 fathoms off Banda Neira in the Molluccas. Dr Willemoes Suhm, in describing the capture, stated that the specimen seemed to have been in the stomach of a fish, as its surface was slightly digested, and he thought it must have habits of concealment which usually prevent its capture, and that it was secured on this occasion only by the capture of the fish which had swallowed it. The fact that the shells are washed ashore in such large numbers is not fully explained. Possibly when freed from the animal the air in the chambers of the shell causes it to float, and in that case it would naturally be sooner or later washed ashore. (J. T. C.)
End of Article: CEPHALOPODA
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