The anatomy of Lottia gigantea Gray. 13 



the two species. In Acmaea patina the lateral walls of the pharynx 

 are much more extensively and intricately folded than in Lottia 

 gigantea and the lateral pockets are deeper. It would seem that the 

 walls are glandular. 



The oesophagus passes nearly directly backward from the pharynx, 

 to slightly beyond the middle of the body, lying beneath the stomach 

 and distal arm of the intestine, and being covered by a portion of 

 the gonad. It turns to the right to enter the fore chamber of the 

 stomach (Fig. 1). After another constriction the canal widens out 

 into the stomach which curves around the liver and, making prominent 

 posterior and anterior elbows, arrives again close to the proventri- 

 culus, and slightly under it. Except in the distal end where it curves 

 downward, the stomach lies in one plane, juxtaposed to the distal 

 arm of the alimentary canal. At the extreme anterior end of the 

 stomach the large liver duct empties into the lumen. Along the 

 ventral wall, and on the opposite side along the dorsal wall, there is 

 a ribbonlike tract, running from the fore end of the stomach well 

 into the intestine, where the epithelium is raised in little close-set 

 crosswise plications, like an "endostyle" (Fig. 17 S). I do not know 

 the function of these ridges. Beyond the stomach the intestine passes 

 forward and makes a turn in the region of the subintestinal ganglion. 

 Turning sharply backward a complete loop is executed under the 

 forward arm of the stomach, and another forward elbow is made, in 

 advance of the previous one, and fairly behind the septum of the 

 head cavity and right buccal gland. From here the course is ob- 

 liquely backward and to the left, under the oesophagus. After an 

 S-shaped turn under the proventriculus the intestine curves upward 

 and forms a final loop around the stomach passing forward and to 

 the right, to open into the mantle cavity immediately to the left of 

 the right nephridial papilla. The course of the canal can be much 

 more easily understood from Fig. 1. The walls of the rectum are 

 folded longitudinally (Fig. E) the folds completing a partial spiral. 

 Two folds are much larger than the others, and the walls of these 

 are in turn plicated. The epithelium is composed of high clearly 

 defined cells with nuclei near the base, a very thin cuticle and abundant 

 cilia, about one-third or a half as long as the cell itself. 



The liver lies in the spaces between the intestine, from the gonad 

 below to the dorsal wall above. It almost completely covers the 

 stomach, and extends forward around the anterior bends of the canal. 



