18 A FLOEA WITHIN ANIMALS. II. 



termination in the rectum, where it is as narrow as the ventriculus. Its parietes 

 present a great number of slight depressions, arranged in quadrangular groups, 

 which latter form longitudinal rows the whole length of the large intestine. 



The rectum {i) is short, elliptical, and presents several narrow internal longi- 

 tudinal folds or elevated lines, continuous with the longitudinal lines of separation 

 of the rows of quadrangular groups of depressions of the large intestine. 



It is within the ventriculus, the large intestine, and the rectum, that the exten- 

 sive Julidean flora and fauna are found. 



§ 2. Of the Anatomy of the Intestinal Canal of Passalus cornutus. 



{Plate VI. Figs. 8-10.) 



The intestinal canal of Passalus cornuius, in accordance with the nature of the 

 animal's food, is capacious, and about three times the length of the body. 



The oesophagus extends in a straight line as far back as the mesothorax, is 

 capacious and claviform, gradually widening to its posterior fourth, and then 

 narrowing to its termination in the proventriculus. 



The latter (PL VI. Fig. 8, a) constitutes about two-thirds of the whole length 

 of the alimentary canal. It makes several transversely circular convolutions within 

 the abdomino-thoracic cavity; it is capacious, and, with the exception of its com- 

 mencement, which is a little dilated, claviform, is nearly uniformly cylindrical 

 throughout. The mucous membrane of the proventriculus, with the exception of 

 a small portion of its posterior extremity, is studded pretty closely with white 

 circular glands, arranged, though not very regularly, in alternating rows ; which, 

 through the translucent parietes of the organ, give it a white maculated appearance. 

 At the junction of the proventriculus with the ventriculus open four biliary 

 tubes. 



The ventriculus (Fig. 8, h ; Fig. 9), which in Passalus always contains entophytic 

 forests, makes a sigmoid turn from the left backwards, and to the right side. It 

 is one-third broader than the proventriculus ; and, for the most part, is constituted 

 of six longitudinal rows of transversely oval sacculi separated by as many inter- 

 vening folds or ridges. The sacculi are about twenty in number, in each row, 

 separated by transverse folds; they open into the interior of the organ (Fig. 10, 

 a). At the commencement of the ventriculus, upon the left side, there projects 

 an oval, curved, coecal pouch (Fig. 9, h), apparently formed by the conjunction of 

 two of the ventricular sacculi, though as large as four of them. Within the ventri- 

 culus, the lateral borders of the longitudinal folds (Fig. 10, h), separating the 

 sacculi, between the transverse folds (c), are thickly set with simple, bidentate, and 

 tridentate, amber-colored, corneous spines (PI. IX. Fig. 1, d). These are arranged 

 in two separate and close columns, convergent forwards, and extending backwards 

 in a straggling manner between the ventricular sacculi. Besides these spines, the 

 surface of the mucous membrane is everywhere studded with distant, stiff, corne- 

 ous, yellow, translucent, hair-like appendages, which, at the edges of the ventri- 



