FOR ZOOLOGICAL PURPOSES.
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Sponges.—To preserve specimens of these merely as museum
specimens it is not necessary to subject them to previous preparation,
but merely to place them in 70 per cent, alcohol, changing the same
several times in order that the specimen may be completely pene-
trated by it.
To prepare dried specimens, wash them first in fresh water for
about two hours, then leave them for a day in strong ordinary
alcohol, and afterwards dry them in the open air or in the sun.
Anthozoa.—The two principal divisions of this group are the
Octactinise or Alcyonaria, and the Hexactiniae, of which the Sea-
anemones are the most familiar representatives.
Alcyonium digitatum, sometimes known as "Dead men's fingers,"
is very common on the British coasts, but it is difficult to preserve
specimens with the polypes well expanded. The method to be
employed is as follows : Place the specimen in clean sea-water until
it is completely expanded, for which one may have to wait a day or
two. The vessel used must be only large enough to contain the
specimen, and when it is expanded the quantity of sea water must be
reduced by means of a siphon until only enough is left to cover the
specimen. Then a mixture is made of acetic acid (pure), 100 parts,
chromic acid (1 per cent. solution) 10 parts, and a quantity of this
mixture twice as great as that of the water containing the specimen
is rapidly poured over the latter. The polypes are thus killed before
they can contract. The specimen is removed after a few seconds
into dilute alcohol of 30 per cent., whence it is transferred into
alcohol of increasing strengths successively until it is in 70 per
cent. A saturated solution of corrosive sublimate, made hot, may
also be used in the same way.
Pennatula and Gorgonia may be killed in a similar manner; or
the former may be taken suddenly when expanded from the sea
water and plunged into the fixing liquid.
Actiniaria.—Sea-anemones are perhaps the most difficult of all
marine animals to prepare either for exhibition or for study. They
are extremely sensitive and very muscular, and the density of the
tissues is such that it is very difficult to kill or paralyse the muscles
before they contract, or to anaesthetize the sensory tissues com-
pletely. It often happens that when the operator believes a specimen
is killed or rendered insensible in the expanded condition, and
transfers it to some other reagent, it begins to contract violently, and
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