110 METHODS OF COLLECTING AND PRESERVING 
Crustacea. 
Cladocera, Copepods, and Schizopods may be killed in corrosive 
sublimate dissolved in sea-water. Ostracods may be thrown at once 
into 70 per cent, alcohol. Cirripeds die expanded in 35 per cent, 
alcohol ; and if some specimens contract, it is easy to draw out 
the cirri with forceps. Amphipods and Isopods may pass directly 
into 70 per cent, alcohol, except the Bopyrids and Entoniscids, 
which should be killed in the mixture of equal parts of 90 per cent, 
alcohol and sublimate solution. 
To avoid the casting off of the appendages of the Decapods, 
they should be allowed to die in fresh-water, care being taken 
not to allow them to remain in it longer than is necessary, as it 
causes a distortion of the membranous appendages. Pycnogonids 
will die in 0"5 per cent, chromic acid, with the appendages fully 
extended. 
Hermit-crabs should be killed in fresh water, when they will come 
out of their shells • if killed in alcohol, it is often impossible to 
extract them without injury. The shells should be preserved with 
any commensals, as Anemones, Hydroids, etc. 
Large Crabs and Lobsters can be preserved dry : their colours are 
best kept by their being dried away from strong sunlight. Specimens 
of the same species should also be preserved in alcohol. 
Formalin should be avoided for Crustacea. It renders the speci- 
mens brittle, and dissolves out a part of the calcareous salts to form 
a flocculent precipitate. 
POLYZOA. 
Polyzoa are horny, calcareous, or gelatinous ; they incrust other 
objects, or form masses or arborescent growths. They are nearly 
all colonial animals, and usually the small separate " zooecia " can 
be made out with the naked eye or with a lens, Polyzoa are mostly 
marine ; but there are also a number of fresh-water species. 
These animals may be preserved in strong spirit or in 10 per cent, 
solution of formalin. 
Specimens can be obtained with polyps expanded by killing sud- 
