KILLING. 17 



24. Chloride or Sulphate of Magnesium.- -TULLBERG (Arch. 

 Zool. Exper. et Gen., x, 1892,, p. 11). For Actinia, a 33 per 

 cent, solution of the chloride should be very slowly added to 

 the water containing the expanded animal, until the vessel 

 contains 1 per cent, of the salt (thus for one litre of sea 

 water 33 c.c. of the solution must be added). The addition 

 must be completed within half an hour, and thirty minutes 

 later the animal may be fixed. 



For terrestrial and fresh-water Invertebrates rather 

 stronger solutions should be used. 



REDENBAUGH (Amer. Natural, xxix, 1895,, p. 399) takes the 

 sulphate, either added in crystals to the sea water containing 

 the animals until a saturated solution is obtained, or in the 

 shape of a saturated solution into which they are thrown 

 (Annelids.) 



See also MAYER, Bid. Bull. Wood's Hole, xvii, 1909, 

 p. 341 (puts direct into sol. of -| strength). 



25. Poisoning by small doses of some fixing agent is sometimes 

 good. Lo BIANCO kills Ascidia and Rlwpal&a in an extended state 

 (Mittli. Zool. Stat. Neapel, ix, 1890, p. 471) by pouring a little 1 per cent, 

 chromic acid on to the surface of the water containing them, and 

 allowing it to slowly diffuse into it. About twelve to twenty-four hours 

 is necessary. He kills dona 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. 



26. 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 they 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 



2 



