GASTEROPODES. 267 



CHAPTER XI. 



GASTEROPODES. 



THE literal interpretation of what constitutes the subject of this 

 chapter, signifies those soft-bodied or molluscous animals which crawl on 

 the belly. This, it will be observed, however, is a restricted view, for 

 there are many which do so that belong to very different branches of the 

 System of Nature. 



A considerable number of such animals having occurred to me in 

 the course of years, I purposed devoting some chapters to them in detail, 

 but circumstances have induced me to confine myself to a few abstract 

 observations. Probably the recent works of accomplished naturalists will 

 more than supply the deficiency. 



It is somewhat doubtful, unless by conventional arrangement, 

 whether a character sufficiently exclusive is taken for the extensive 

 genera and species to be comprehended under Gasteropodes. But that is 

 of less importance here, as I shall speak of only some of the animals 

 formerly constituting the extensive genus Doris, after a sentence or two 

 on the Aplysia, as a suitable introduction. 



All the subjects of this chapter are very nearly akin to the Limacine 

 tribe, of which one peculiar characteristic is, crawling on the under sur- 

 face of the body, and, in this respect, the name is perhaps more appro- 

 priate than either Trachelipodes or Cephalapodes, the one applying to 

 those inhabitants of shells whose flesh fills the spiral, and those whose 



