12 KILLING 



sea water and 1 of 10 per cent. sol. of chloreton in absolute alcohol, 

 for Scyllium and Anguilla. 



For Bryozoa, see Bessie Green, Journ. Roy. Mic. Soc, 1914, 



19. Hydrate of Chloral. Foettinger {Arch, de Biol., vi, 

 1885, p. 115) operates by dropping crystals of chloral into the 

 water containing the animals. For Alcyonella he takes 25 to 80 

 centigrammes of chloral for each 100 grm. of water. It takes 

 about three-quarters of an hour to render a colony sufficiently 

 insensible. He has obtained satisfactory results with marine 

 and fresh-water Bryozoa, with Annelida, Mollusca, Nemertians, 

 Actiniae, and with Aster acanthion. He did not succeed with 

 Hydroids. 



Lo Bianco {Mitth. Zool. Stat. Neapel, Bd. ix, 1890, p. 442) 

 employed for various marine animals freshly prepared solutions 

 of chloral in sea water, of from j\y to ^ per cent, strength. 



We have never had the slightest success with Nemertians. 



Verworn {Zeit. wiss. Zool., xlvi, 1887, p. 99) puts Cristatella for a 

 few minutes into 10 per cent, solution of chloral, in which the animals 

 sooner or later become extended. 



KuKENTHAL {JcTia Zeit. Naturw., Bd. xx, 1887, p. 511) has obtained 

 good results with some Annelids by means of a solution of 1 part of 

 chloral in 1,000 parts of sea water. 



The chloral method gives rise to maceration with some subjects, 

 and has been said to distort nuclear figures. 



20. Cocaine (Richards, Zool. Anz., cxcvi, 1885, p. 3327). 

 Richards puts a colony of Bryozoa into a watch-glass with 5 c.c. 

 of water, and adds gradually 1 per cent, solution of hydrochlorate 

 of cocaine in water. After five minutes the animals are some- 

 what numbed ; ^ c.c. of the solution is added, and 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. It is the best method for Rotifers (Rousselet). 

 It has also been recommended for Aplysia. 



It has been pointed out (by Cori, in the paper quoted § 17) 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. 



21. Eucain. Harris {Journ. Roy. Mic. Soc, 1900, p. 404) 

 reconnnends a 1 per cent, solution of eucain hydrochloride, as 

 giving far better results, with Vorticellidae, Rotatoria, and Vermes. 

 Rousselet {ibid.) reports favourably as to its action on 

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

 It dissolves in sea water to about 0-5 per cent. 



