132 A Guide to the Zoological Collections in the 



though equally important in function, is so far as size is 

 concerned, subordinate: it. has the form of a funnel or 

 siphon (whence the name of the sub-Class), through 

 which the water taken into the mantle-cavity is forcibly 

 expelled for the purpose of locomotion. 



The mantle is very complete and very muscular ; it 

 encloses a wide and deep mantle-chamber, in which the 

 gills are placed, and into which the intestine and the 

 excretory and reproductive organs open. 



Except in the Octopodes, a true shell secreted by the 

 mantle is present, and although sometimes, e.g., Nautilus, 

 the shell encloses the body, it usually is itself enclosed and 

 entirely concealed in a dorsal fold of the mantle, and 

 becomes an "internal shell": in this case it is sometimes, 

 as in the Squid, a rudiment of quill-like form and paper- 

 like consistency. 



The Siphonopods possess, besides the characteristic 

 odontophore, a pair of horny or calcareous jaws, shaped 

 like a parrot's beak, specimens of which are shown in 

 Case 170. The sexes are distinct. 



The spirit specimens and dissections of a common Indian 

 species of Cuttle-fish, placed above Case 170, give a good 

 illustration of the Cephalopod type. 



An examination of this series shows the animal to 

 consist of a somewhat rounded head, and an oval or 

 conical body, the shape of which is determined by the 

 thick fleshy mantle. The skin both of the head and body 

 is thickly set with large pigment-ceils, or " chromato- 

 phores", the play of which in life leads to transient 

 chameleonic changes of colour. 



The edge of the mantle projects round the base of 

 the head like a collar, the intervening space being the 

 entrance into the mantle-chamber. From the head S2:)ring 

 the long fleshy prehensile arms, or prolongations of the 

 fore part of the foot : these are ten in number, and are 

 beset on their inner surface with most beautifully formed, 

 cup-shaped, cartilaginous suckers arranged in rows. In 



