~ 
MOLLUSCA. 2) 
ficiently expressive, though too uncouth for general 
adoption, that of HETEROGANGLIATA.* 
All the senses common to the higher animals 
are found in the Mouuusca, though some are, 
doubtless, wanting in the humbler Classes of the 
Division: In the Cephalopoda, the organs of sight 
and hearing are distinct and well developed, and 
Professor Owen is of opinion that the Nautilus, an 
animal of this Class, possesses an organ of “passive 
smell.” The Gasteropoda are almost invariably 
furnished with eyes; and, according to M. Siebold 
and other zoologists, with ears also, a pair of round 
capsules, placed near the bases of the tentacles, and 
enclosing one or more crystalline globules, called 
otolites. Some of the Conchifera are furnished with: 
numerous eyes, placed among the tentacles, ex- 
amples of which are found in the Clams and 
Scallops (Pecten) of our own shores. I scarcely 
know a more beautiful sight of the kind, than is 
presented by the edges of the mantle in one of our 
Scallops. If you ever have an opportunity of pro- 
curing a living specimen, which is not difficult to 
find at low water, on most of our rocky shores, 
place it in a glass of sea-water, and watch its 
movements. Soon the beautiful painted shells will 
begin to open, and the fleshy mantle will be seen 
to occupy the interval, like a narrow veil extending 
perpendicularly from each shell. The edge of each 
of these veils will now be seen, if you examine it 
with a pocket lens, to be fringed with long white 
threads, which are the tentacles, or organs of touch ; 
and amongst them lie scattered a number of minute 
points, having the most brilliant lustre, and bearing 
a close resemblance to tiny gems. Indeed, the 
* That is, “having dissimilar nerve-knots.” . 
to} 
