The question with which we have next to deal is, after collecting a
number of living mollusks, how, in the quickest and most painless
manner possible, to kill the animals in order to obtain possession of
their shells. There is but one way we know of in which this may be
accomplished, and that is by placing the creatures in an earthen jar
and pouring _boiling_ water on them. With land, or fresh-water snails,
the addition of a large spoonful of table-salt is advisable, as it
acts upon them chemically, and not only puts them sooner out of pain,
but also renders their subsequent extraction far easier. Death by this
process is instantaneous, and consequently painless; but to leave
snails in cold salt water is to inflict on them the tortures of a
lingering death; while for the brutality of gardeners and other
thoughtless persons who seek to destroy the poor snail they find
eating their plants by crushing it under foot on the gravel path, no
words of condemnation are too strong, since it must always be borne in
mind that snails have not, like us, _one_ nervous centre, but three,
and are far more tenacious of life; hence, unless all the nerves are
destroyed at once, a great deal of suffering is entailed on the poor
creature; and if merely crushed under foot, the mangled portions _will
live for hours_. Hot water has also the advantage of tending to remove
the dirt which is almost sure to have gathered on the shells, and so
helping to prepare them better for the cabinet. As soon as the water
is cool enough, fish out the shells one by one and proceed to extract
the dead animals. This, if the mollusk is _univalve_ (_i.e._, whose
shell is composed of a single piece), such as an ordinary garden
snail, can easily be done by picking them out with a pin; you will
find, probably, that some of the smaller ones have shrunk back so far
into their shells as to be beyond the reach of a straight pin, so it
will be necessary to bend the pin with a pair of pliers, or, if none
are at hand, a key will answer the purpose if the pin be put into one
of the notches and bent over the edge until sufficiently curved to
reach up the shell. You will find it convenient to keep a set of pins
bent to different curves, to which you may fit handles by cutting off
the heads and sticking them into match stems. It is a good plan to
soak some of the smaller snails in clean cold water before killing
them, as they swell out with the water, and do not, when dead, retreat
so far into their shells. If you have a microscope, and wish to keep
the animals till you have time to get the tongues out, drop the bodies
into small bottles of methylated spirit and water, when they will keep
till required, otherwise they should of course be thrown away at once.
The now empty shells should be washed in clean warm water, and, if
very dirty, gently scrubbed with a soft nail or tooth brush, and then
carefully dried.
In such shells as the Periwinkle, Whelk, etc., whose inhabitants close
the entrance of their dwelling with a trap-door, or _operculum_ as it
is called, you should be careful to preserve each with its proper
shell.
If you are cleaning _bivalves_, or shells composed of two pieces, like
the common mussel, you will have to remove the animal with a penknife,
and while leaving the inside quite clean, be very careful not to break
the ligament which serves as a hinge; then wash as before, and tie
them together to prevent their gaping open when dry.
Sometimes the fresh-water or marine shells are so coated over with a
vegetable growth that no scrubbing with water alone will remove it,
and in these cases a weak solution of caustic soda may be used, but
very carefully, since, if too strong a solution be employed, the
surface of the shell will be removed with the dirt, and the specimen
spoilt. In some shells the periostracum is very thick and coarse, and
must be removed before the shell itself can be seen; but it is always
well to keep at least one specimen in its rough state as an example.
In other shells the periostracum is covered over with very fine,
delicate hairs (_Helix sericea_ and _Helix hispida_, Fig. 3), and
great care must then be taken not to brush these off.
[Illustration: Fig. 3. (_a_) _Helix sericea_ and
(_b_) _Helix hispida_.]