CLASS CEPHALOPODA. 75 



internal skeleton, whicli is enclosed within the thick skin 

 of the body. This skeleton (fig. 31, B) has something ot 

 the form of a paddle or of a feather, and it is generally 

 known as the "pen." It is of a horny consistence, semi- 

 transparent, and consisting of a central stem with two 

 lateral expansions or " wings." In old specimens there 

 are several of these "pens," packed closely one behind 



the other. . 



The Calamary, as before mentioned, lives in the sea, and 

 the present species is generally distributed round the shores 

 of Great Britain. Where abundant, it is used by the 

 fishermen as bait. In the quaint language of Pennant, 

 these animals "inhabit all our seas; are gregarious; swift 

 in their motions ; take their prey by means of their arms, 

 and embracing it, bring it to their central mouth. Adhere 

 to rocks, when they wish to be quiescent, by means of the 

 concave discs that are placed along their anns." They 

 appear to Hve upon shell-fish, and sometimes sea-weed, and 

 they lay their eggs in clusters containing many thousands. 



Eecapitulation of Essential Characters. — Of the 

 above-mentioned characters which distinguish the Cala- 

 mary, the foUowing are essential : The body is symmet- 

 rically constructed, so that you could divide the animal 

 with a knife into two halves, which would externally be 

 exactly similar to one another. The mouth is placed m 

 the front of the head, and is surrounded by a circle of mus- 

 cular processes or " arms." The breathing-organs are m 

 the form of giUs ; and the water which has passed over the 

 gills is expelled from the body by means of a muscular 

 tube or "funnel." By the jet of water thus emitted, the 

 animal can propel itseK through the water. The mouth 

 is furnished with beak-like jaws, and also with a tongue, 

 the hinder part of which is provided with bent spines. 

 The nervous system is highly developed, and is partially 

 protected by what may be regarded as a rudimentary 

 skull. These characters distinguish all the animals which 

 are related to the Calamary, and they may therefore be 

 taken as the distinctive characters of the entire class of 

 the Ceiyhalopoda. 



