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See also:OCTOPUS (Gr. brcreo, eight and gobs, See also:foot) , the name in scientific See also:zoology belonging to a single genus of eight armed See also:Cephalopoda (q.v.), one of whose distinguishing characters is that it has two rows of suckers on each See also:arm . This true See also:octopus occurs occasionally on the See also:British coasts, at least the See also:south See also:coast, but is usually rare . It is more See also:common on the See also:southern coasts of See also:Europe, including those of the Mediterranean . The usual See also:species of Octopoda on the British south coast is Eledone cirrosa, which has only one See also:row of suckers on each arm, and is a smaller See also:animal . The celebrated See also:account of the octopus given by See also:Victor See also:Hugo in his Travailleurs de la mer is not so fictitious as some critics with a knowledge of natural See also:history have maintained . It is true that the See also:great See also:French author has made the See also:mistake of using the name Cephaloptera, which belongs to a large tropical See also:fish similar to a skate, instead of Cephalopoda, and that he applies the See also:term See also:devil-fish, which belongs to Cephaloptera, to the octopus . His description is exaggerated, imaginative and sensational; but it is correct in its most important particulars, and bears See also:evidence that the author was to some extent personally acquainted with the animal and its habits, although he was not a scientific observer . The octopus feeds on crabs, and crabs feed on carrion, and, therefore, there is nothing impossible in Hugo'saccount of the See also:skeleton of a drowned See also:man surrounded by the shells of See also:numbers of crabs which the octopus had devoured . Whether an octopus would attack and kill a man is another question, but it certainly might seize him with its arms and suckers while holding to the rocks by other arms, and a man seized in this way when in the See also:water might be in danger of being drowned . The octopus and many of the Octopoda move about by means of their arms on the See also:sea bottom, and are not See also:free-See also:swimming, though like other Cephalopods they can propel themselves on occasion backwards through the water by means of the See also:funnel . Other Octopoda, however, are pelagic and free-swimming, and such habits are not confined to those forms which are provided with lateral fins . The Argonaut (see See also:NAUTILUS) is one of the Octopoda . The separation of one of the arms of the male for purposes of See also:reproduction is one of the most remarkable peculiarities of the Octopoda . It does not occur, however, in octopus nor in many other members of the See also:group . One arm is always considerably modified in .structure and employed in copulation, but it is only in three genera, one of which is Argonauta, that the arm spontaneously separates . The detached arm is found still alive and moving in the See also:mantle cavity of the See also:female, and when first discovered in these circumstances was naturally regarded by the older naturalists as a See also:parasite . See also:Cuvier, on account of the numerous suckers of the detached arm, gave it the name Hectocotylus (See also:hundred suckers) . When the arm is not detached but only altered in structure it is said to be hectocotylized . In Octopus and Eledone it is the third right arm which is hectocotylized . The extremity of this arm is See also:expanded and assumes the shape of a See also:spoon . Whether detached or not the modified arm possesses a cavity into which the spermatophores are passed and the arm serves to convey them to the mantle cavity of the female . It has been mentioned above that the true octopus (Octopus vulgaris) is usually rare on the See also:English coast . In 1899 and 1900, however, they became so abundant on the south coast as to attract See also:general See also:notice, and to constitute a veritable See also:plague which threatened See also:complete ruin to the See also:shell-fish See also:fisheries . This visitation and its effects were described by W . Garstang in the See also:Journal of the Marine Biological Association . The abnormal abundance occurred all along the See also:west coast of See also:France, whence it extended to the Channel, and was probably due to a See also:succession of unusually warm summers and mild winters, beginning with the warm See also:spring and hot summer of 1893 . The octopus in the years mentioned entered the See also:lobster pots of the fishermen and devoured or killed the crabs and lobsters captured . The pots when hauled contained usually only living octopus and the mutilated remains of their victims . One fisherman took in a single See also:week 64 specimens of octopus and only 15 living uninjured lobsters . The octopus also almost exterminated the swimming crabs (See also:Portunus) in See also:Plymouth See also:Sound, and in the tanks of the Plymouth See also:aquarium attacked and devoured all the specimens of its smaller relative Eledone cirrosa . With regard to the See also:size which the octopus may attain, the dimensions of the See also:body are not usually given in records, but it is stated that the arms in the largest specimens measured 31 ft., and in numerous cases were 3 ft. in length . This would enable the eight arms to extend over a circle 6 ft. in See also:diameter, but the globular body is not more than about a third of the length of n_ arm in di'ameter . When not in pursuit of See also:prey the octopus hides itself in a hole between rocks and covers itself with stones and shells . Like its victims it seems to be active chiefly at See also:night and to remain in its See also:nest during the See also:day . For a technical account of the Octopoda see CEPHALOPODA; also W . Garstang," The Plague of Octopus on the South Coast, and its Effect on the Crab and Lobster Fisheries," Journ . See also:Mar . Biol . Assoc. vol. vi . (19oo) p . 260 . (J . T . |
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