CEPHALOPODS. 4/5 



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 Onychotenthis, 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 p>ower- 

 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 



