254 Description of a Species of Caligus. 
IV. Nurririve 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 aninchlong. 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 contails 
