ON MOLLUSCA. 201 
The mode of nutrition in the malacozoaria is in general 
much less known than that of their locomotion. 
A very small number can seize their prey before they intro- 
duce it into the buccal cavity. To effect this, the singular 
appendages with which their head is provided interlace and 
attach themselves very closely, by the aid of the sort of cup- 
ping-glasses with which they are furnished, to the living 
animal which is about to be devoured. 
The mollusca whose buccal orifice is furnished with teeth 
appear to be able to seize and chew their food with them. 
When there is but one tooth above it serves as a resting point 
on which the lingual swelling acts in its anterior part, which 
is very observable in the limaces, helices, and approximating 
genera. 
We are not equally well acquainted with the mode of action 
of the proboscis in such mollusca as are provided with one. 
It is believed, however, that the teeth with which it is often 
armed at its extremity, when it is sufficiently unrolled, may 
serve to make a hole in the shell of other mollusca, through 
which this proboscis may be introduced to tear or suck the 
soft parts ; but this is very far from being indubitably ascer- 
tained. 
The mollusca feed on all kinds of substances, animal or 
vegetable, in all states, living or dead, fresh or putrified; but 
each species, and even each genus, but less certainly each 
family, confines itself to one or other kind of these aliments. 
All the known cryptodibranchia are nourished upon living 
animals, which they tear, and perhaps break, but which pro- 
bably they do not masticate. 
The siphonobranchia appear also to be all carnivorous ; but 
it is probable that they rarely swallow their prey entire, but 
that they suck it, draw it into their proboscis, armed or un- 
armed, but that they do not chew it, being unprovided with 
organs adapted for true mastication. 
