THE LIVING SPECIMENS IN THE AQUARIUM. 
109 
Limpets are eligible inhabitants to admit to your little salt-water world. 
They are eminently quiet and self-contained, and sometimes their shells 
are veiy prettily marked. Ihose should be chosen that are found ad¬ 
hering loosely to the rocks, with 
the shell raised some little dis¬ 
tance from the body; for when 
they are firmly fixed to rocks 
and stones, and have to be dis¬ 
lodged with some degree of force, 
they are likely to become injured 
and die. It is best to choose those 
which have a sea-weed growing 
from the shell; for then you have limpet. 
a sort of multum in pcirvo —several specimens in one. 
Such animals as the limpet, and others resembling it, belong to a species 
of mollusks called gasteropoda, which are so named from their locomotive 
organs being attached to the under part of their bodies. They are, how¬ 
ever, to a certain extent, armed against attack or danger by a shelly covering. 
There is another class of mollusks that creep about without any such pro¬ 
tection, and whose gills, or lungs, instead of being inside, are exposed on 
the exterior of their bodies. These are hence called nudibranches , or naked- 
gilled mollusks. The Doris and Eolis are types of this class. The gills of 
the former are spread out in an arborescent form, and have a most elegant 
V 
THE EOLIS. 
effect. The latter has these organs branching out over its entire body, 
like semi-transparent quills, giving a most remarkable appearance to the 
animal, as it glides along. Both are to be found adherent to the under sur¬ 
face of stones, etc. 
The writer had always been led to believe that these animals were very 
voracious, and, indeed, that “ a wolf would be about as appropriate an inmate 
of a sheep-fold, as one of them in an aquarium, where sea-anemones live.” 
Naturally, in consequence of this sweeping assertion against the beautiful 
eolis, he watched his specimen with considerable attention for several 
weeks, and came to the conclusion that he had been shamefully libelled by 
sundry writers. But, that this opinion on his part was premature, he one 
day discovered. Happening to give my usual peep into the tank before 
going to bed, I saw plainly that my eolis “ was no better than he should 
be,” and that the charge of greed brought against him was perfectly cor¬ 
rect. I was therefore obliged to come to the conclusion that his quiet, 
