248 NAKED CEPHALOPODS. PART in. 



transparent ; the surface immediately below it consists 

 of numerous cells, of a flattened oval or circular form, 

 containing coloured particles suspended in a liquid. 

 The colour is seldom the same in all these cells; the 

 most constant kind corresponds with the tint of the 

 inky secretion. In the Sepia there is a second series of 

 cells, containing a deep yellow or brownish colour ; in 

 the common Calamary, or Squid, there are three kinds 

 of coloured cells yellow, rose-coloured, and brown ; 

 and in the Poulpe there are red, yellow, blue, and black 

 cells. The cells possess the power of rapid contraction 

 and expansion, by which the coloured liquid is drawn 

 into deeper parts of the surface, and is again brought 

 into contact with the semi-transparent skin thus con- 

 stantly varying. In consequence of the high develop- 

 ment of the nervous system, the skin of the Naked 

 Cephalopods is of extreme sensibility ; a mere touch 

 brings a blush on that of the Poulpe, and they all 

 assume the colour of the surface on which they rest as 

 readily as the chameleon. Many of these nocturnal 

 animals are luminous, and are easily attracted by bright 

 metallic objects. 



