Description of a Species of Caligus. 255 



several muscular bands, which connect the opposite crenations ; in 

 their contraction the crenations are rendered more prominent. 

 These muscles are connected by other slender muscles irregularly 

 arranged, which contract the stomach longitudinally. The lateral 

 portions of the stomach are connected on each side with the shell 

 adjoining, by ligamentous or cellular attachments, as is represented 

 in fig. 9. There is no valve between the stomach and the intes- 

 tine, and when the peristaltic motion is reversed, as often happens, 

 the fluids frequently return into the stomach. 



The intestine, at its commencement, is between three and four 

 times the diameter of the esophagus, and about one fifth the di- 

 ameter of the stomach. It is slightly enlarged below the second 

 pair of natatories, where there are two pairs of glands, contracts 

 again as it passes below the apron, and thence continues of uni- 

 form size to the rectum. Its structure is very similar to that of 

 the stomach, both in its inner and outer coat. The arrangement 

 of its muscles in regular bands is represented in fig. 11 ; during 

 their action the canal is crenated as in the figure. The intestine 

 is attached by distinct ligaments at several places ; near the 

 glands, d, and the glands, e and f, we have distinctly seen these 

 attachments. 



The rectum occupies the terminal half of the last abdominal 

 segment, and is about one half the diameter of the intestine. Its 

 communication with the intestine, is closed in the natural state of 

 the parts. This rectum, if it may be so called, appears to have a 

 longitudinal opening below, extending its whole length and its 

 walls are usually in close contact. The external opening or anus 

 is situated at its extremity. 



This portion of the alimentary canal is opened laterally by 

 seven pairs of slender muscles. The first pair at the extremity 

 pass directly outward along the margin of the joint ; the second 

 are inserted near the extremity, and pass upward and a little 

 outward. The following three pairs, are attached near the mid- 

 dle, and pass outward and a little upward ; the remaining two 

 pairs, are inserted near the opening to the intestine, and have the 

 same direction as the last. The muscles have often been seen in 

 action, in expelling the faeces ; the two sides move either simulta- 

 neously or alternately, according to the necessity of the case, in 

 the act of expulsion. 



