2 MOLLUSCA. 



the surrounding soft or fleshy matter. But the propriety 

 of abandoning the old divisions will become sufficiently 

 obvious, when we consider that all the species belong 

 to one group in the invertebrate class of animals ; 

 that the organs of the species have many points of 

 resemblance ; and that although differences prevail in 

 the character of the protecting covering, the gradations 

 from one condition of the integuments to another, are 

 too minute, in many cases, to admit of precise limits being 

 fixed. We shall therefore consider shells as peculiar mo- 

 difications of the external coverings of certain species, and, 

 in this subordinate character, incorporate the naked and 

 shelly species ; having recourse to the integuments, how- 

 ever, in connection with the other organs, in the distribu- 

 tion of the genera and other divisions of the class now 

 denominated MOLLUSCA. 



In treating of this extensive division of the invertebrate 

 animals, we shall confine our remarks to a general view of 

 their physiology, taking notice of the peculiarities of their 

 forms, organs, and functions. This will prepare us for a 

 condensed view of the progress of the science, in reference 

 to systematical arrangement, and the illustrations of the 

 characters of those divisions or groups into which the spe- 

 cies may be distributed, whether for assisting the student 

 in his labours of investigation, or for facilitating the judici- 

 ous disposition of the established truths of the science. We 

 shall then advert, in the last place, to molluscous animals 

 as objects of utility. The limits of the article will unavoid- 

 ably restrict us to a very brief exposition of the various 

 subjects connected with this very extensive department of 

 natural history. 



