ANATOMY OF PALUDESTRINA 



161 



members of the genus. It is lined by a cuticle which is fairly 

 thin ventrally, but becomes thicker dorsally. This cuticle is 

 secreted by a columnar epithelium which is continuous with 

 that of the lips and adjacent parts. Each cell of this epithelium 

 contains an elongate, deeply-staining mass of secretion which 

 occupies the major portion of the cell and usually obscures 

 the nucleus. These secretion-masses are especially well 

 developed where the cuticle is deepest ; and in these areas the 



Text-mg. 1. 



Transverse section through the mouth, c, cuticle ; m, mandibles ; 

 se, secretory epithelium. 



whole epithelium is characterized by a mass of extra-cellular 

 pigment in the shape of very small, subcircular granules. 



In the upper portion of the mouth is found a pair of man- 

 dibles. These consist of a number (minimum 13, maximum 20) 

 of columnar pieces of specialized cuticle, each secreted by 

 a single cell of the basement epithelium, as Seibold found in 

 Vitrella (20). That the secretion-masses are intimately con- 

 cerned in the formation of these is shown by the fact that 

 plates are often continuous with the former. The mandibular 

 plates stain very sharply with eosin, the rest of the cuticle 

 being more or less unaffected by the stain. There is sometimes 

 present, in addition to the mandibles, a specialized piece of 



