A 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 Moxuusca. 
Tn 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 greups 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. 
