RESPIRATION AND DIGESTIVE APPARATUS. 



341 



generally present remarkable dilatations (c6), interwoven with 

 muscular fibres, so as to form two contractile reservoirs, perform- 

 ing the functions of pulmonary hearts. This arrangement is 

 observable in all Cephalopods with two gills ; but does not exist 

 in those which are provided with four. It may be regarded as 

 a transition-form between the heart of the lower Mollusca, which 

 is altogether systemic ( 874) ; and that of Fishes, which is 

 entirely respiratory ( 535). 



880. The digestive apparatus is very complicated. The 

 mouth is surrounded by a circular lip ; and the parrot-like jaws 

 are put in motion by powerful muscles.. There are well-developed 

 salivary glands, several stomachs, and a voluminous liver ; the 

 intestine terminates in the branchial cavity, at the base of the 

 funnel by which the water is ejected, and communicates with a 

 very singular secreting organ, which, in the dibranchiate (two- 

 gilled) Cephalopods, produces an abundance of a black liquor, 

 commonly termed its ink. The 



duct of this gland opens near 

 the anus; and, when the animal 

 is in danger, it expels this liquid 

 through the funnel in sufficient 

 quantities to hide the animal 

 from the view of its enemies, 

 by mingling with the surround- 

 ing water. It is the ink of 

 one of these animals, the Cuttle- 

 fish, which is employed in 

 painting, under the name of 

 Sepia ; and several authors 

 look upon Indian Ink as an 

 analogous substance. The 

 four-gilled Cephalopods present 

 nothing of this kind. 



881. The arrangement of the Flo< 543._ LoL iGopsis. 

 organs of locomotion, which 



are fixed around the mouth, varies in different divisions. In the 

 two-gilled Cephalopods, there is a crown of large fleshy tentacula, 

 whose internal surface is provided with suckers, by means of 



