158 MANUAL OF THE MOLLUSCA. 



times free all round, and it is supported only by cartilaginous 

 ridges, fitting into corresponding grooves, and allowing con- 

 siderable freedom of motion. 



The cuttle-fishes are generally nocturnal, or crepuscular 

 animals, concealing themselves during the day, or retiring to a 

 lower region of the water. They inhabit every zone, and are 

 met with near the shore, as well as in the open sea, hundreds of 

 miles from land. They attain occasionally a much greater size 

 than any other mollusca. MM. Quoy and Gaimard found a dead 

 cuttle-fish in the Atlantic, under the equator, which must have 

 weighed 2 cwt. when perfect ; it was floating on the surface, 

 and was partly devoured by birds. Banks and Solander also 

 met with one under similar circumstances in the Pacific, which 

 was estimated to have measured six feet in length. (Owen.) 

 The arms of the octopods are sometimes two feet long.* From 

 their habits, it is difficult to capture some species alive, but 

 they are frequently obtained, uninjured, from the stomachs of 

 dolphins and other cetaceans which prey upon them. 



Section A. — Octopoda. 



Arms, eight ; suckers sessile. JEyes fixed, incapable of rotation. 

 Body united to the head by a broad cervical band. Branchial 

 chamber divided longitudinally by a muscular partition. Oviduct 

 double ; no distinct nidamental gland. SheU internal and 

 rudimentary. 



The Octopods differ from the typical cuttle-fishes in having 

 only eight arms, without the addition of tentacles ; their bodies 

 are round, and they seldom have fins. 



The males and females have a general resemblance to each 

 other ; although the form and appearance of the sexes are very 

 distinctive. But until recently our knowledge on the subject 

 has been confused. In all male cuttle-fishes one of the eight 

 arms presents a peculiar appearance and undergoes a special 

 development, fitting it for the purpose of helping forward the 

 work of reproduction of the species. In many cases it is so 

 altered as to be incapable of acting as a locomotive organ. 

 According to Dr. Miiller, the arm is detached, after it has been 

 filled with semen, and is fixed on to the female. The arm, or 

 •whatever it may be that is so attached, was formerly mistaken 



* Denys Monffort, having represented a " kraken octopod," in the act of scu'tling a 

 three-master, told M. Defrance that if this were " swallowed," he would in his next 

 edition represent the monster embracing the Straits of Gibraltar, or capsizing a whole 

 equadron of ships. (D'Orbigny). 



