VARIOUS INVERTEBRATE ANIMALS. 
119 
process employed by Professor Van Beneden. The corm is placed in 
clean sea-water for a few hours. When the zooids are extended, the 
corm is seized with the fingers and dropped into glacial acetic acid, 
and left there for from two to six minutes. It is then removed with 
the fingers, and washed well in 50 per cent, alcohol, and graded into 
successively stronger alcohols up to 70 per cent. This method avoids 
the use of steel, and will not injure the fingers if they are washed 
at once. 
Mollusca. 
L am el 1 i branch s and Heteropods should be narcotized in alcoholized 
sea-water. To avoid the closure of the valves of Lamellibranchs 
on immersion in 70 per cent, alcohol, little pings of wood should be 
placed between the margins of the valves. '1 he same result may 
be effected in the case of large Prosobranchs after narcotization by 
tying the operculum to the shell. 
Of the Opisthobranchs the Solids may be best preserved by 
pouring over them concentrated acetic acid in volume equal to 
or double that of the sea-water containing them. Dorids should 
first be narcotized by gradually adding 70 per cent, alcohol to their 
sea-water, and then killed with concentrated acetic acid or boiling 
sublimate. The larger forms may be killed in from 1 to 5 per 
cent, chromic acid. 
Pteropods are preserved well in Perenyi’s fluid for fifteen minutes^ 
whence they are passed to 50 per cent, alcohol. Gymnosomatous 
forms should be first narcotized with 1 per cent, chloral hydrate, and 
then killed in acetic acid or sublimate. 
Decapod Cephalopods may be fixed directly in 70 per cent, alcohol, 
if an opening be made on the ventral surface to allow the alcohol to 
reach the internal parts. After twenty-four hours the alcohol 
should be poured off and replaced by a fresh quantity. After three 
days’ immersion in this second quantity of alcohol, it is recommended 
that Cephalopods be preserved in 5 per cent, formalin, formalin 
does not destroy the pigments of the integument. 
