CEPHALOPODA. 59 
armed with a pair of horny or calcareous mandibles, 
which bear a strong resemblance to the bill of a 
parrot, acting vertically one upon the other. Its 
situation is the bottom of a subconical cavity, 
formed by the base of the numerous fleshy tenta- 
cular appendages which surround it, and which have 
been termed arms by some naturalists, and feet by 
others.” 
These fleshy flexible feet are characteristic of the 
Class, and give to it its systematic appellation of 
Cephalopoda, signifying head-footed. They are 
instruments of locomotion; the animal being enabled 
to crawl awkwardly upon this circle of feet, head 
downwards. But their chief use to the animal is 
as organs for the seizing and holding of prey; 
and for this purpose they are eminently qualified. 
Each arm is furnished with a double row of sucking 
disks, each of which on being applied to any surface 
adheres to it at the will of the animal with immense 
force, so that it is easier to tear away the substance 
of the limb while the creature maintains its hold, 
than to release it from its attachment; and even 
after death, the suckers continue to retain a con- 
siderable power of adhesion. 
The manner in which these suckers act, will be 
understood by a reference to the principle of a 
cupping-glass. Hach one consists of a firm fleshy 
or cartilaginous ring, across which a disk of 
muscular membrane is stretched, with a circular 
aperture in the centre. A cone-shaped mass of 
flesh fills this aperture, like a piston, capable of 
being drawn backward. The membranous disk 
itself can also be drawn in. Now, let us suppose 
that one of the sucking disks of a tentacle touches 
any object fit for prey, such as a fish, for example, 
