GASTEROPODES. 267 
CHAPTER XI. 
GASTEROPODES. 
Tue 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 
