FOR ZOOLOGICAL PURPOSES.
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Tunicata.—Appendicularia should be placed for five minutes
in the chrom-osmic mixture.
Clavellina and Perophora are placed in chloral hydrate 1 per
thousand for six to twelve hours, and then killed with the mixture
of ten parts chromic acid 1 per cent. to 100 parts pure acetic acid.
Ciona intestinalis is killed by adding the same mixture drop by
drop to the vessel of sea water in which it is expanded ; in about
half an hour it is dead, and it is then transferred to chromic acid, 1
per cent., some of the same being injected into its interior with a
pipette, and after about half an hour it is transferred to weak
alcohol.
Of the compound Ascidians, Botryllus is best killed by nar-
cotizing in chloral hydrate 1 per thousand, for an hour or two, and
then killing with a flood of hot solution of sublimate.
Fishes.—Lo Bianco recommends both for Elasmobranchs and
Teleostei simple immersion in 70 per cent. alcohol, an incision being
made in the wall of the abdominal cavity, and the alcohol being
injected into the cavity and changed repeatedly. But I have found
that with Teleostei this method causes contraction of the tissues and
folds in the skin, and that cold solution of corrosive sublimate is a
much better reagent. After the fish have been in the sublimate
solution for half an hour to two hours they must be washed for
an hour or more in a current of fresh water and then transferred to
70 per cent. alcohol. Dog-fishes are best hardened in 1/2 per cent.
solution of chromic acid for some hours, with injection into the body
cavity, then washed and transferred to alcohol. The colours of
Teleosteans are not preserved in spirit, but may be kept to some
extent in their original condition by placing the specimens after sub-
limate and washing, in glycerine and water, changing them constantly
into less diluted glycerine, and finally keeping them in pure glycerine-
The embryos of Elasmobranchs, skates, and dog fishes, may be
fixed either in sublimate solution for about fifteen minutes, or in
chromic acid 1 per cent., being washed in fresh water before they are
transferred to alcohol.
GENERAL RULES TO BE OBSERVED.
In practising the methods above described there are certain
principles which must be constantly remembered. Except in the
few cases where a greater strength is recommended, alcohol of the