CEPHALOPODOUS HOLLUSCA. 171 



excrement! tious ; and that the liver is partly an eliminating 

 organ, destined to separate impure carbonaceous materials 

 from the blood. 



[ 321. In the CEPHALOPODA the mouth is situated in the 

 centre of the tentacular circle, and armed with two horny 

 jaws, resembling the bill of a parrot, imbedded in the flesh, 

 and moved by powerful muscles. In the interior of the 

 mouth is a moveable cartilaginous tongue ; the pharynx, 

 lodged at the anterior part of the cephalic cartilage, is 

 very large and muscular ; the long and straight esophagus 

 is surrounded by the nervous collar ; the stomach, like that 

 of Aplysia, presents three enlargements, forming a crop, a 

 gizzard, and a true digestive stomach. The crop is a dilata- 

 tion of the esophagus, leading into the second globular sto- 

 mach ; it is very muscular, and communicates by a narrow 

 opening with the third, or true digestive cavity, remarkable 

 for possessing a singular spiral valve, formed by a fold of the 

 lining membrane winding round its inner surface ; a modi- 

 fication of structure which we shall find repeated in some 

 cartilaginous fishes, with which the cephalopoda are closely 

 connected in many points of organization. Into this third 

 chamber the ducts from the liver and pancreas pour their 

 several secretions. The short intestinal canal, commencing at 

 the pyloric orifice of the third stomach, ascends in front 

 of the liver, and terminates in a valvular opening within 

 the funnel, situated at the under part of the neck. The 

 liver in the whole of this class is very large, and its copious 

 secretion is poured by two ducts, along with the vessel, from 

 the follicular pancreas into the third stomach, their orifices 

 being provided with a valvular apparatus ; the salivary glands, 

 four in number, insert their superior pair of ducts into the 

 pharynx, and their inferior pair into the esophagus. 



The naked cephalopods, as the cuttle-fish, have a peculiar 

 black, inky fluid, prepared by the glandular lining membrane 

 of a particular bag, provided with a duct opening into the 

 funnel. This fluid is secreted in great abundance, and being 

 very miscible with water, forms a black cloud when injected 

 into the sea ; and by means of this singular provision these 

 naked, defenceless animals are enabled to elude the pursuit 

 of their numerous enemies. The inky fluid, abounding iu 



