254 Description of a Species of Caligus. 



IV. Nutritive System. 



a. Organs of digestion. 



The alimentary canal, (fig. 9, PL V,) is composed of three dis- 

 tinct parts, corresponding to the esophagus, the stomach and the 

 intestine. 



The esophagus constitutes one sixth the whole length of the 

 alimentary canal, and in large individuals is about one sixteenth 

 of an inch long. It extends in the form of a long slender tube of 

 uniform diameter to the stomach, and passes a short distance into 

 its cavity. Its insertion in the buccal mass may be seen in fig. 

 17, which is an under view of this organ. The anterior opening 

 is closed by two fleshy folds, which have already been described 

 when speaking of the organs and muscles of the buccal mass. 

 At its commencement, there is an oblong enlargement, (fig. 

 10,) longitudinally striated, which may be considered a pharynx. 

 The communication with the stomach is closed, but whether by 

 a sphincter or valve is undetermined. The peristaltic motion fre- 

 quently seen in the stomach and intestine, never extends into the 

 esophagus. 



This portion of the alimentary canal is readily separated into 

 two membranes. The inner, the mucous coat, is thin and trans- 

 parent, and very smooth. The outer is much thicker, and scarcely 

 semi-transparent ; its muscular fibres are not apparent. When, 

 highly magnified, its exterior surface appears very uneven. If 

 the mouth is detached from the body with care, the esophagus often 

 continues attached to it, and presents the appearance exhibited in 

 fig. 17. The inner coat is usually entire to its termination in the 

 stomach, while the outer which is continuous with the exterior 

 membrane of the stomach is invariably torn off, not far from the 

 base of the esophagus, as in the figure. 



The stomach has a broad cordate form, and is a little shorter 

 than the esophagus, and when expanded is somewhat wider than 

 long ; vertically it is quite narrow. The anterior extremity lies 

 between the prehensile legs, and posteriorly it extends under the 

 furcate process on the venter. The lateral margin is very deeply 

 crenated, owing to the peculiar arrangement of its muscles. The 

 teguments of the stomach are composed of the same coats as the 

 esophagus, and they present the same general character. The 

 inner appears uniformly smooth and even. The outer contains 



