290 Introdiictioii to A7iimal Morphology. 



gelatinous tissue and fusiform or stellate cells* (the Chia- 

 jean organ, or the organ of Delle Chiaje), opens into the 

 oesophagus in some genera. 



The stomach is usually simple, thin-walled, pouch- 

 like, rarely four-angled, with four tooth-like pro- 

 jections (Pterotrachea), often with caecal pouches 

 projecting from it towards its cardiac or pyloric ends ; 

 its epithelium is columnar (Heteropoda), or ciliated in • 

 tracts, and often elevated into tooth-like processes 

 (Telescopium), or lobular projections (Mitra). It is 

 gizzard-like in Aplysia, with cartilaginous pyramids 

 in its wall, and is lamellated with cartilage plates in 

 Umbrella. The folds of its lining may be armed with 

 hard epithelial cutting ridges (Tritonia, Scyllaea). In 

 Philine the large stomach fills half the body cavity, 

 and has three bony plates in its wall. Scaphander 

 has similar three-sided plates with rounded angles. 

 The beginning of the intestine in Aplysia, Tethys, 

 and Pleurobranchus is dilated, in Aplysia, hidden in 

 the liver, and is sometimes regarded as a third sto- 

 mach. The intestine is short, ciliated, simple, and 

 ends, usually forwards and on the right side, rarely 

 posteriorly (Vaginulus, Onchidium), in an often wart- 

 like anus, never lying in the respiratory cavity. Its 

 wall consists of a muscular stratum, mostly of circular 

 fibres, but with longitudinal intermixed, not in sepa- 

 rate layers, often with oval, calcareous concretions 

 freely scattered in it. The rectum is differentiated in 

 Prosobranchs, and is often dilated and longitudinally 

 folded within on the right side of the mantle cavity. 

 The intestine is shortest in flesh-eaters like Buccinum, 

 sometimes straight, with no flexure.f In Pulmonates 



* Dolium, Murex, Buccinum, Voluta, Conus, Pleurobranchus. 

 t Apneusta, Phlebenterata. 



