138 bulletin: museum of compakative zoology. 



The change from the esophageal epithelium to that of the stomach 

 is very sharp, although it is accompanied by no change in the 

 topography of the canal. The rather clear, ciliated cells of the 

 esophagus proper give place to the peculiar granular cells — the 

 cytoplasm of which is closely packed with minute vacuoles of 

 secretion — so characteristic of the intestine. These are inter- 

 spersed with very slender cells, each with a few cilia of greater 

 length than are found in the esophagus. In the anterior portions 

 the nuclei of the ciliated cells lie near the free borders of the cells, 

 but farther posteriorly sink into their inner portions. The cilia in 

 this posterior region are few, but of a length almost equal to that of 

 the cell itself. 



The folds in the ventral walls of the stomach become gradually 

 more marked, and their lining of epithelium gradually differentiated 

 to form the intestine proper. There is, therefore, no sharp line of 

 demarcation between these two portions of the alimentary canal, 

 either anatomically or histologically. In the intestine proper, which 

 begins somewhat anterior to the sexual glands, the cells conform 

 closely to the type described for other species, and are largely filled 

 with the usual minute vacuoles of secretion. 



The walls of the intestine are thrown up into conspicuous folds, 

 with deep and slender pockets between them. Whether these 

 pockets should be looked upon as permanent diverticula or merely 

 as temporary depressions is somewhat uncertain. In transverse 

 sections (PI. 9, fig. 59; PI. 10, fig. 63) it becomes evident that the 

 depressions certainly do not correspond with the paired diverticula 

 of Carinoma and the higher forms, for the ejiithelium of the cen- 

 tral canal passes gradually into the deepest depressions, and there 

 are no fibrous partitions between the pouches. A longitudinal sec- 

 tion (PI. 10, fig. 65) shows that the folds and their intervening 

 depressions concern the epithelial lining only, and in no way affect 

 the thin fibroiis layer making up the wall of the canal outside the 

 epithelium. The relation of the pouches is shown also in a tan- 

 gential section (PI. 10, fig. 64) through the distal portions of the 

 pouches. This shows incipient secondary folds (inf") between the 

 principal ones. 



The height of these epithelial folds of the intestine depends 

 largely on the degree of contraction of the body, and would doubt- 

 less become largely obliterated if the body were stretched to its 



