126 THE PRESERVATION OF MARINE ANIMALS
solution of sublimate. They may be taken out of the sea water
separately with a pipette, or may be filtered out by means of fine
muslin, or may be killed by simply adding the sublimate solution to
the water in which they are swimming, afterwards decanting the
mixture and replacing it with pure sublimate solution. Whenever
sublimate is used for killing, the specimens should be washed for a
long time, e.g., an hour, in fresh water before being placed in alcohol.
Mollusca.—Lamellibranchs must be narcotized in sea water
and alcohol (5 parts of the latter to 100 of former), remaining in
it six to twelve hours, by which time they will usually be insensible,
with the foot and siphons extended; then they can be transferred to
70 per cent. alcohol. It is well to place a piece of wood between
the valves of the shell to prevent them closing again.
Gasteropods, such as Patella, Buccinum (whelk), etc., are to be
treated in the same way. Another method which succeeds well with
some species of Natica, and with Nassa and Trochus, is to place the
animals for some days in a mixture of sea water and fresh water in
equal parts, and then fix them with acetic acid.
Among Opisthobranchs Elysiidae and Eolididae are to be killed
suddenly with pure acetic acid poured over them while expanded in
a small quantity of sea water, and as soon as they are dead they must
be transferred to weak alcohol.
Doris and allied forms must be first narcotized by adding 70 per
cent. alcohol to the sea water containing them, and then suddenly
killed with a flood of acetic acid or boiling sublimate. Large speci-
mens of Tritoma are to be placed in fresh water to which are added
some drops of acetic acid till they are dead, and are then placed in
chromic acid 1/2 per cent.
Cephalopoda.—The Octopods, such as Eledone or Octopus, are
killed in chromic acid 1 per cent., in which they remain half an hour
to two hours; they are then washed in fresh water, from which they
are transferred to alcohol 70 per cent., changed repeatedly. Decapods,
such as Loligo, Sepia, Sepiola, can be fixed in the same way, or
directly in alcohol 70 per cent, care being taken to draw out the two
tentacular arms as soon as the animal is dead.
Polyzoa.—Many species can be killed in the expanded con-
dition, like Hydroids, with a flood of hot solution of corrosive sub-
limate. Other methods which sometimes succeed better are adding
70 per cent. alcohol to the sea water, or placing the specimens in
chloral hydrate, 1 per thousand, before placing them in sublimate.