KILLING. 15 



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

 employs for various marine animals freshly prepared solu- 

 tions of chloral in sea water, of from one tenth to one fifth 

 per cent, strength. 



I am bound to state that I have never had the slightest success with Ne- 

 mertians. 



VEEWOEN (Zeit. f. wiss. Zool., xlvi, 1887, p. 99; see also Journ. Roy. 

 Mic. Soc., 1888, p. 148) 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 ; Journ. Roy. 

 Mic. Soc., 1888, p. 509) has obtained good results with some Annelids by 

 means of a solution of one part of chloral in 1000 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. 



19. Cocaine (RICHARDS, Zool. Anz., 196, 1885, p. 332) has 

 been found to give good results. Richards puts a colony of 

 Bryozoa into a watch-glass with 5 c.c. of water, and adds 

 gradually I per cent, solution of hydrochlorate of cocaine in 

 water. After five minutes the animals are somewhat numbed, 

 and 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 certain worms. It is the best method for Rotifers 

 (ROUSSKLET). It has also been recommended for Aplysia. 



It has been pointed out (by GOBI, in the paper quoted above) that unfor- 

 tunately when fixing agents, such as sublimate solution, are added to the 

 animals, the cocaine is thyown down on them as a white precipitate. This 

 precipitate, however, may be redissolved afterwards in alcohol (EisiG). 



19a. Menthol (SoRBY, Flcreanus, Sheffield, 1898, No. 4, p. 68 ; Journ 

 Roy. Mic. Soc., 1899, i,p. 103). Sorby finds that by adding a small quan- 

 tity of menthol to the sea water in which " marine animals " (which ?) are 

 kept, they fully expand themselves and die in a " distended " condition. 

 He has thus succeeded with Synapta and several species of sea-anemones. 



20. Hydroxylamin. HOFEU (Zeit. f. wis*. Mik., vii, 3, 1890, 

 p. 318) has employed hydroxylamin as a paralysing agent 

 with success with the most varied animal forms. Either the 

 sulphate or the hydrochlorate of the base may be used. He 

 recommends that the hydrochlorate be taken. This, as found 



