CEPHALOPODA. 



47 



held on to the body by two of the arms, which are dilated and 

 specially adapted for this purpose. Only the female Argonaut is 

 provided with a shell, the male being shell-less and a much smaller 

 creature. The Argonaut-shell is therefore not a true shell, but 

 simply a receptacle for the ova, serving at the same time for the 

 protection of the parent. 



Cliiroteiithis Veranyi is remarkable on account of the great length 



Fiff. 42. 



Chiroteuthis Veranyi (much reduced). 



a, general view of animal ; b, magnified view of pedunculated sucker of the 

 terminal club of the tentacular arms ; c, internal shell or gladius. 



of the tentacular arms. These are non-retractile and are employed 

 to seize their prey when at a distance. 



Species of Polypus are found on the shores of almost all temperate 

 and tropical seas ; they do not attain to a large size, and are without 

 the internal shell or " bone " which is found in the mantle of many 

 Cephalopods. That of the Cuttlefish or Sepia (Fig. 43 a) is found in 

 abundance on our coasts ; it is composed of numberless layers of a 

 friable calcareous substance. That of the Squid tribe, termed the 

 gladius, is of quite another character, consisting of an elongate thin 

 horny plate, and strengthened by one or more thickened ribs, in some 

 species somewhat resembling a quill-pen. Some species of this pen- 

 bearing class related to the Common Squid attain an immense size. 



