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. yes fixed, incapable of rotation. 
Body united to the head by a broad cervical band. Branchial 
chamber divided longitudinally by amuscular partition. Oviduct 
double; no distinct nidamental gland. Shell internal and 
rudimentary. 
The Octopods differ from the typical cuttle-fishes in haying 
only eight arms, without the addition of tentacles ; their bodies 
are round, and they seldom have fins. 
The males and females haye 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 Montfort, having represented a “‘ kraken octopod,” in the act of scuttling 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 whols 
squadron of ships. (D’Orbigny). 
