CHAPTER II. 15 



certain worms. It is the best method for Rotifers (ROUSSELET). 

 It has also been recommended for Aplysia. 



It has been pointed out (by Com, in the paper quoted 18) that, 

 unfortunately, when fixing agents, such as sublimate solution, are 

 added to the animals, the cocaine is thrown down on them as a white 

 precipitate. This precipitate, however, may be redissolved afterwards 

 in alcohol (EisiG). 



Cocaine solutions cannot be depended on to keep for more than a few 

 days. 



22. Eucain. HARRIS (Journ. Roy. Mic. Soc., 1900, p. 404) 

 recommends a 1 per cent, solution of eucain hydrochloride, as giving 

 far better results, with Vorticellidse, Rotatoria, and Vermes. 

 ROUSSELET (ibid.) reports favourably as to its action on Flosculariae. 

 It is stated to be perfectly stable in aqueous media. It dissolves in 

 sea water to about 0-5 per cent. 



23. Hydroxylamin. HOFER (Zeit. wiss. Mik., vii, 1890, p. 318). 

 Either the sulphate or, preferably, the hydro chlorate 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 0*1 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. 



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

 Exper. et Gen., x, 1892, p. 11). For Actiniae, 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, Bid. Bull. Wood's Hole, xvii, 1909, p. 341 (puts 

 direct into sol. of f strength). 



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

 good. Lo BIANCO kills Ascldia and Rhopalcea in an extended state 

 (Mitth. Zool. 8tat. Neapel, ix, 1890, p. 471) by pouring a little 1 per cent. 



