Introduction to Animal Morphology. 313 



CHAPTER XXXVIII. 



CLASS 3. CEPHALOPODA. 



MARINE, carnivorous, dioecious, symmetrical molluscs, 

 the highest of the sub-kingdom ; with partially cleft 

 ova ; a distinct head surrounded by the modified foot ; 

 ration branchial ; sense-organs well developed ; 

 the bodies are antero-posteriorly shortened and verti- 

 cally elongated ; they creep with the head downwards, 

 and swim laterally with their upper side forwards. 



The integument is smooth, rarely papillose, covered 

 by a porous cuticle of united cylinder (Nautilus) or 

 pavement cells, on a basis of fibrillar tissue, beneath 

 which are one or two layers* of nucleated pigment 

 cells with contractile processes (chromatophores). 

 The' pigment is rarely in the surface epithelium. f 

 Under these is often a layer of lamellar, highly re- 

 fracting corpuscles (jUttcrchcn^} producing by inter- 

 ference a play of colours. 



M'-neath these layers, loose connective tissue covers 



a muscular and connective substratum, containing 



usually a network of capillary blood-vessels. The in- 



vent of the sides of the body is differentiated into 



a mantle which incloses a cavity whose opening is 



ted downwards -backwards in progression), and 



which lii-s on tin- posterior [or what is generally con- 



of differed 



:nc of those 



- 



.Mid tO 



Ihcsc Jlittei 



