KILLING. 17 



diffuse into it. About twelve to twenty-four hours is necessary. He kills 

 Ciona in a similar way with a mixture of one part of 1 per cent, chromic 

 acid and nine parts of 49 per cent, acetic acid. 



Osmic acid, or Kleinenberg's solution, is sometimes employed in the 

 same way. 



I have seen Medusae killed in a satisfactory manner by means of crystals 

 of corrosive sublimate added to the water containing them. 



Morphia, Curare, Strychnin, Prussic Acid, and other paralysing 

 drugs have also been employed. 



23. Asphyxiation may be sometimes successfully practised. 

 Terrestrial Gastropods may be killed for dissection by putting 

 them into a jar quite full of water that has been deprived of 

 its air by boiling, and hermetically closed. After from 

 twelve to twenty-four hours the animals are generally found 

 dead and extended. The effect is obtained somewhat quicker 

 if a little tobacco be added to the water. 



Good results are sometimes obtained with aquatic animals 

 by simply leaving them to exhaust the oxygen of the water in 

 which they are contained. I have sometimes succeeded with 

 Holothuriaa and other Echinoderms in this way. WARD (see 

 Amer. Nat., xxv, 1891, p. 398) has succeeded with Hydroids, 

 Actiniae,, and similar forms, and UEXKULL (Mitth. Zool. Stat. 

 Neupel, xii, 1896, p. 468) with Echinids. If the animals be 

 found to be imperfectly expanded when narcosis has set in, 

 they may be got to expand by putting them back for a short 

 time into pure sea water ; and as soon as they are expanded 

 should be quickly thrown into some rapidly killing reagent. 



Marine Animals are sometimes successfully killed by simply 

 putting them into fresh water. 



Warm Water will sometimes serve to immobilise and even 

 kill both marine and fresh-water organisms. 



24. Carbonic Acid Gas has been recommended (by FOL, Zool. 

 Anz.,, 128, 1885, p. 698). The water containing the animals 

 should be saturated with the gas. The method is stated to 

 succeed with most Coelenterata and Echinodermata, but not 

 with Molluscs or Fishes. I have had most excellent results 

 with small Annelids and Hirudinea. It is not necessary to 

 employ a generator for obtaining the gas. It suffices to take 

 an ordinary " soda-water " siphon, and squirt its contents 

 into the water containing the animals. 



2 



