14 KILLING. 



CORI (Zeit. wiss. Mik., vi, 1890, p. 438) recommends a mixture 

 composed of 10 c.c. methyl-alcohol (of 96 per cent, strength), 90 c.c. 

 water (fresh or sea water), and 0-6 grm. of sodium chloride (to be 

 added only when fresh water is taken, the addition of the salt having 

 for its object to prevent maceration). It may be well to add to this 

 mixture a very few drops of chloroform (for Cristatella ; Zeit. wiss. 

 Zool, Iv, 1893, p. 626). 



19. Chloreton (Aceton Chloroform) is recommended for inverte- 

 brates and larvae of Rana by RANDOLPH (Zool. Anz., xxiii, 1900, 

 p. 436). KRECKER (Zeit. wiss. Zool., xcv, 1910, p. 383) takes 

 solutions of J to 1 per cent, for Oligochseta. SULIMA (Zeit. Biol. 

 Techn., Strasburg, i, 1909, p. 379) takes a mixture of 99 parts of 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. 



20. 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 centi- 

 grammes of chloral for each hundred grammes 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 Asteracanthion. He did not succeed with Hydroids. 



Lo BIANCO (Mitth. Zool. Stat. Neapel, Bd, ix, 1890, p. 442) employs 

 for various marine animals freshly prepared solutions of chloral in 

 sea water, of from -^ to ^ per cent, strength. 



I 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 (Jena 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, 

 as I can testify, and has been said to distort nuclear figures. 



21. Cocaine (RICHARDS, Zool. Anz., cxcvi, 1885, p. 332). 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 somewhat numbed; 

 half a cubic centimetre 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 



