KILLING 13 



22. Hydroxylamin. Hofer {Zeit. wiss. Mik., vii, 1890, p. 318). 

 Either the sulphate or, preferably, the hydroehlorate may be used. 

 This should be dissolved in water (spring or sea water, according to the 

 habitat) and exactly neutralised by addition of carbonate of soda. The 

 organisms are placed in a solution diluted to about 01 per cent., for 

 thirty minutes or less (as for Infusoria), to 0-25 per cent., for from 

 fifteen minutes to one hour (Hydra), 1 per cent., one half to two hours 

 (Hirudo) or as much as ten to twenty hours (Helix and Anodonta). 



Hydroxylamin is a powerful reducing agent, and should therefore be 

 well washed out before treating with easily reducible fixing agents. 



23. Chloride or Sulphate of Magnesium. Tullberg (Arch. 

 Zool. Exper. et Gen., x, 1892, p. 11). For Actinise, 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 1 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, Biol. Bull. Wood's Hole, xvii, 1909, p. 341 

 (puts direct into sol. of 70 per cent, strength). 



24. Poisoning by small doses of some fixing agent is sometimes good. 

 Lo Bianco kills Ascidia and Rhopalcea in an extended state (Mitth. 

 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 diffuse slowly into it. About twelve to twenty-four 

 hours is necessary. He kills Ciona in a similar way with a mixture of 

 1 part of 1 per cent, chromic acid and 9 parts of 49 per cent, acetic 

 acid. 



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

 same way. 



Lee has 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. 



25. 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 closing it. 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. We have sometimes succeeded with Holo- 



