Anatomy and Physiology of Anodonta Fluviatilis. 179 



attached to the surrounding mass (PL 6, fig. 1, i. e.). The intestine 

 thence turns abruptly toward the right side of the body. The portion of 

 the intestine last described is somewhat larger than that first described, 

 being about two millimetres in diameter, and at the point where it turns 

 toward the right side it becomes somewhat clavate in shape, and is 

 three millimetres in diameter : after turning to the right side it almost 

 immediately turns toward the dorsal and posterior part of the body, 

 crossing the portion first described nearer to the right side, con- 

 tinuing in this direction for the space of twenty millimetres, then 

 curving toward the anterior. At this part the intestine is small, 

 being about one millimetre in diameter. Almost immediately beyond 

 the point where the direction of the curvature is toward the anterior, 

 the intestine turns toward the left side and abruptly enlarges to a 

 diameter of about five millimetres and continues nearly to the dorsal 

 margin, parallel to and nine millimetres from that portion of the 

 intestine proceeding from the stomach toward the post-ventral margin 

 of the body. The intestine gradually becomes smaller as it approaches 

 the dorsal surface, at that point being a little more than three milli- 

 metres in diameter; it here turns abruptly backward, leaving the 

 body and passing through the ventricle, though entirely unconnected 

 with that organ, thence over the posterior adductor muscle, and ending 

 just beyond that muscle, opening into the cloacal chamber, 

 . The intestine after leaving the body is called the rectum (PI. 6, r.), 

 the opening at the extremity is the anus (PL 6, a.). 



The lining membrane of the intestine, throughout its entire length, 

 has numerous strong transverse folds. On that portion of the intestine 

 nearest to the ventral margin, a ridge commences which continues to 

 the extremity. 



Digestion takes place in the stomach, and the nutritive matter 

 evolved transudes through the walls of the intestine and thus enters 

 the system. 



The Labial Palpi. 



(Plate 13.) 



The labial palpi consist of two pairs of thin contractile, foliated 

 lobes, two on each side of the body (PL 13, fig 5, 1. p.). They are 

 subtriangular in outline. The widest portion situated posteriorly. 

 The following measurements are of the palpi of an animal eight cen- 

 timetres in length : length, 17 mm., width at posterior portion, 8 mm. ? 

 rapidly narrowing to the oral cavity (PL 11, fig. 3). The outer 

 lamina passes above the mouth, the inner below, each becoming con- 

 tinuous with its fellow on the opposite side, and continuous with the 

 lining membrane of the mouth and forming lips to that organ (PL 13, 



