'J'HE OAENIVOKOUS SLUGS OF SOUTH AFRICA. 177 



intestine is considerably narrower in A. burnupi and A. 

 sexangula than in the other species. 



In Apera dimidia and A. purcelli the first curve of 

 the intestine lies in a more nearly vertical plane, and does not 

 extend so far towards the right side (PI. IX, fig. 29, and 

 PI. XXI, fig. 132). Then, after curving down on the 

 left side, the intestine continues backwards on that side of 

 the liver instead of on the right (cf. PI. X, tig. 32, and 

 PI. XI, figs. 34, 35). 



Beyond the region of the liver the alimentary canal con- 

 tinues backwards as the rectum beneath the mantle-cavity. 

 It is at first suriounded by the funnel-shaped prolongation 

 of the body-cavity, but further back it curves towards the 

 right side of the animal, and bends up the right Avail of the 

 mantle-cavity on reaching the level of the respiratory opening. 

 As will be seen from PI. X, fig. 33, the anus is immediately 

 below the respiratory opening, and the space between them 

 is partially separated from the rest of the mantle-cavity by 

 an oblique fold of the wall of the cavity, which projects 

 forward on the left side of the space. 



The epithelium lining the intestine is composed of very 

 irregular columnar cells, the appearance of which is well 

 shown in PI. XXII, fig. 137. The inner walls of these cells 

 are produced into a delicate fringe of extremely minute cilia. 

 Outside the epithelium there is a thin layer of circular muscles, 

 and external to this a thin layer of longitudinal mu^scles. The 

 structure of the rectum is very similar to that of the 

 intestine, excepting that the epithelium is normally thrown 

 into deep folds (PI. XXII, fig. 136). At the anus, however, 

 the epithelial cells become more regular and oblong in section, 

 and their cilia become far longer and less delicate. 



The Salivary Glands and Ducts. — The salivary glands 

 are fairly compact, and are situated above and on each side 

 of the crop near its junction with the oesophagus. There are 

 always two glands, but in Apera gibbonsi and A. dimidia, 

 and to some extent in A. parva and A. purcelli, they are 

 united above the crop, as in so many of the carnivorous snails 



