CEPHALOPODS: 475 
mantle, according to Cuvier, united beneath the body, thus forming 
a muscular sac which envelopes the whole viscera. The body is soft 
and fleshy, varying much in form, being sub-spherical, sub-elliptical, 
and cylindrical, the sides of the mantle in many species extending into 
fleshy fins. The head protrudes from the muscular sac, and is dis- 
tinct from the body ; it is gifted with all the usual organs of sense, the 
eyes in particular, which are either pedunculate or sessile, being large 
and well developed. The mouth is anterior and terminal, armed 
with a pair of horny or calcareous mandibles, which bear a strong 
resemblance to the bill of a parrot, acting transversely, one upon the 
other. Its position is the bottom of a sub-conical cavity, forming 
the base of numerous fleshy tentacular appendages which surround it, 
and which are termed arms by some writers. These appendages in 
the great majority of living species are provided with suckers, 
acetabula (cupping-glass-like appendages), by means of which the 
animal moves at the bottom of the sea, head downwards, or attaches 
itself to its prey. These suckers are armed or unarmed with a long, 
sharp, horny claw. In the unarmed acetabula, the mechanism for 
adhesion is well described by Dr. Roget. “The circumference 
of the disc,” says this writer, “is raised by a soft and turned margin ; 
a series of long slender folds of membrane covering corresponding 
fascicula of muscular fibre converge from the circumference towards 
the centre of the sucker, at a short distance from which they leave a 
circular aperture ; this opens into a cavity which widens as it descends, 
and contains a cone of soft substance rising from the bottom of the 
cavity, like the piston of a syringe. When the sucker is applied to 
the surface for the purpose of adhesion, the piston, having previously 
been raised so as to fill the cavity, is retracted, and a vacuum pro- 
duced, which may be still further increased by the retraction of the 
plicated portion of the disc.” Here we have an excellent description 
of the apparatus for holding on. When the animal is disposed to let 
go his hold, according to Professor Owen, “the muscular arrange- 
ment enables it to push forward the piston, and thus in a moment 
destroy the vacuum which retraction had produced.” 
In the case of the Cephalopods, with the arms and tentacles 
armed, as Onychoteuthis, Professor Owen remarks, “that there are 
circumstances in which even the remarkable apparatus described by 
Dr. Roget would be insufficient to fulfil the offices in the economy of 
Nature for which the Cephalopod was created, and that in species 
which have to contend with the agile mucous fishes more power- 
ful organs of prehension are superadded to the suckers, so that in the 
armed Calamary the base of the piston is, he remarks, enclosed in a 
