12 KILLING. 



gradually 1 per cent, solution of hydrochlorate of cocain 

 in water. After five minutes, the animals are somewhat 

 numbed, and half a cubic centimetre of the solution is added, 

 and the tentacles are caused to contract by irritating them 

 with a needle. Ten minutes later the animals should be found 

 to be dead in a state of extension. 



This method is stated to succeed with Bryozoa, Hydra, 

 and certain worms. 



16. Morphia, Curare, Strychnin, Prussic Acid, and other para- 

 lysing drugs have also been employed. 



17. 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 Ccelenterata and Echinodermata, but not 

 with Molluscs or Fishes. 



18. Asphyxiation may be sometimes successfully practised. 

 Terrestrial Gastropods are best killed for dissection by put- 

 ting 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. 



19. Poisoning by small doses of some fixing agent is some- 

 times a good method. SALVATORE LO BIANCO employs the 

 following method for preserving Ascidiae in an extended state. 

 A 1 per cent, solution of chromic acid acidulated with acetic 

 acid is poured on to the surface of the water containing the 

 animals, and allowed to diffuse slowly through it. The opera- 

 tion takes four or five days (v. GARBTNL, Manuale per la Tech- 

 nica Mod. del Microscopio, p. 168). 



Osmic acid, or Kleinenberg's solution, is sometimes em- 

 ployed 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. 



20. Marine Animals are sometimes successfully killed by 

 simply putting them into fresh water. 



21. Warm Water will sometimes serve to immobilise and 

 even kill both marine and fresh-water organisms. 



