VARIOUS SOFT-BODIED INVERTEBRATE ANIMALS. 105 
superfluous water is drawn off, and a saturated solution of picric acid 
is added suddenly ; if a precipitate of cocaine is thrown down, it is 
removed, and fresh picric acid added, the Medusa being left in for 
half an hour, and finally treated with 5 per cent., and later 10 per 
cent., solution of formalin. 
Larger Medusae (Pelagia, Rhizostoma, etc. ) are killed by adding to 
the sea-water in which they are swimming 3 per cent, of a 1 per 
cent, solution of osmic acid. As soon as they begin to assume a 
pale brown tint, they are washed in fresh-water for two minutes, and 
put into 35 per cent, alcohol, and later into 70 per cent, alcohol. 
Mr. Hornell,* of Jersey, reports favourably on 5 per cent, formalin. 
For larvae of ScyphomedusaB [Scyphistoma, Strobila) Signor Lo 
Bianco recommends killing with warm corrosive sublimate, washing 
in fresh -water, and grading into spirit. 
Ctenophora. 
Small forms are treated with osmic acicl and alcohol, according to 
the method given above for the large Medusas. 
Signor Lo Bianco recommends that they should be killed by 
allowing them to fall into chrom-osmic acid mixture (100 ccm. of 
1 per cent, chromic acid and 2 ccm. of 1 per cent, osmic acid), and 
allowed to remain in for from fifteen to sixty minutes, according 
to size, and then graded into alcohol up to 70 per cent. 
Formalin should not be used for preserving Ctenophora. 
Anthozoa. 
The first care must be to place the forms belonging to this 
group in fresh salt-water, to allow them to expand — a result 
which may not be obtained in some cases for twenty-four hours. 
Alcyonarians should be killed with chrom-acetic solution No. 2,f 
withdrawing the water in which they lie until there is left just 
enough to cover them, and then adding a volume of the chrom- 
acetic solution double that of the sea-water. The animals should be 
* Hornell, " Natural Science," 1895, VII., p. 416. 
f Concentrated acetic acid 100 ccm., 1 per cent, chromic acid 10 ccm 
