VAtliOtJS INVERTEBRATE ANIMALS. Il9 



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 hix 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 fingei-s if they are washed 

 at once. 



MOLLUSCA. 



Lamellibranchs and Heteropods should be narcotized in alcoholized 

 sea-water. To avoid the closui-e 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. The 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-wafer contnining 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 ponied ofi' and replaced by a fresh C|uantity. 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. 



