FOR ZOOLOGICAL PURPOSES.
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hydrate in sea water of one part in 1,000. After six to twelve hours
they are hardened in alcohol in long zinc boxes with a layer of wax
at the bottom, being placed in extended position with a glass rod or
similar implement, and if necessary fixed with pins stuck in the wax.
In some cases the process may be much shortened by employing
chloral hydrate at a strength of 1 per cent.
Sagitta may be well fixed in a mixture of 10 per cent. solution of
sulphate of copper 100 parts, sublimate saturated ten parts, or in
chromic acid 1 per cent. 100 parts, osmic acid 1 per cent. two parts.
Leeches, e.g., Pontobdella, are to be killed in chromic acid 1/2 per
cent., extending them with a pin at each end in a dish with a wax
bottom.
Polychaeta, the more common marine worms of which so many
species occur everywhere, succeed well when anaesthetized in a
mixture of five parts of alcohol to 100 sea-water. They are to be
left in this until they lose sensibility, which takes from two to twelve
hours, and then may be hardened in alcohol 70 per cent., or in
chromic acid 1 per cent. It is well to harden them first of all in a
dish with wax bottom where they can be straightened, and to finish
them in long glass tubes. They should be finally preserved in
alcohol of 90 per cent. Worms which live in tubes must be carefully
extracted before they are killed. Serpulids and some others can be
made to quit their tubes by being placed in chloral hydrate one per
1,000, after which they are placed in cold saturated solution of corro-
sive sublimate and then washed in fresh water.
Crustacea.—The larger Decapods, such as crabs, are to be
killed first in fresh water, care being taken not to leave them after
they are dead, and are then placed directly in alcohol 70 per cent.
The hermit-crabs (Paguridae) should be transferred several times to
fresh alcohol, and finally kept in 90 per cent.
Amphipods and Isopods can be placed directly in alcohol of 70
per cent.
To prepare Cirripedia such as Lepas (the Barnacle), they are
allowed to die in 35 per cent. alcohol, when in most cases the cirri
will remain extended; if not they can be gently pulled out with
forceps. Balanus (the Acorn Barnacle) is placed directly in 70 per
cent. alcohol.
Copepoda and marine Cladocera such as Evadne, Schizopoda
such as Mysis, the larvae of Decapods, and even the smaller adults
such as the shrimp, Hippolyte, etc., are best killed with saturated