PATELLA. 221 



traced outwards through the thickness of the crop wall. 

 The transverse folds are infoldings of the side walls 

 between the longitudinal folds just mentioned. They 

 connect with the single divided longitudinal fold, but 

 not with the pair of longitudinal folds. Each of these 

 folds has seeondaiy foldings on itself, and these run 

 approximately along lines radiating from the centre of 

 the crop. Near the inner and free edge of the fold are 

 smaller papilla-like outgrowths (fig. 18). 



The stomach is lined by columnar epithelium, with 

 subjacent connective tissue which is not very abundant. 

 The epithelium is fairly even all round except along a 

 line on the internal wall where we find a groove formed 

 by the upgrowth of two ridges. The height of these 

 ridges is due mainly to the unusual height of the 

 epithelium along them, while the cells lining the groove 

 are very short (fig. 20). This description is correct 

 for a young limpet, but as the animal grows older the 

 groove deepens. 



Much of the intestine has ridged walls. The rectum 

 shows two ventro-lateral folds, which are covered by 

 fairly high columnar epithelium, growing into its cavity 

 and forming a gutter between them. These folds become 

 much more distinct on the anal papilla (fig. 21), and here 

 they branch into secondary foldings. Faeces seem to be 

 extruded only from the upper section of the rectum, 

 dorsal to the " gutter " and folds. 



The buccal glands are made up of much branched tubes 

 which are imbedded in connective tissue, and the glands, 

 for this reason, have the appearance of one large mass. 

 The cells lining the gland tubules are large and contain 

 numerous granules, they are fairly equal in size and have 

 large and distinct basal nuclei. The cells near the apices 

 of the tubules appear not to be ciliated, but those further 



