10 KILLING. 



some time, through the tube, and the animals are then left for 

 some hours in order that narcotisation may become fully estab- 

 lished. The animals are irritated from time to time by touch- 

 ing a tentacle with a needle. As soon as it is observed that 

 an animal begins to react slowly, that is to say as soon as it is 

 found that the contraction of the tentacle does not begin until 

 a considerable time after it has been irritated by the needle, 

 the narcotisation may be considered sufficient. A quantity of 

 some fixing liquid sufficient to kill the animals before they 

 have time to contract is then added to the water. 



A space of several hours is necessary in order to thoroughly 

 narcotise an Actinia by this method. 



10. Nicotin in solution may be used instead of tobacco smoke 

 (ANDRES, Atti R. Accad. dei Lincei, v. 1880, p. 9; see Journ. 

 Roy. Mic. floe., N.S., ii, 1882, p. 881). Andres employs a 

 solution of 1 gramme of nicotin in a litre of sea-water. The 

 animal to be anaesthetised is placed in a jar containing half a 

 litre of sea- water, and the solution of nicotin is gradually con- 

 ducted into the jar by means of a thread acting as siphon. 

 The thread ought to be of such a thickness as to be capable of 

 carrying over the whole of the solution of nicotin in twenty- 

 four hours. 



11. Chloroform may be employed either in the liquid state 

 or in the state of vapour. KOROTNEFF (Mitth. Zool. Stat. 

 Neapel, v, Hft. 2, 1884, p. 229; Zeit. f. iviss. Mik., 2, 1885, p. 

 230) operates in the following manner with Siphonophora. 

 The animals being extended, a watch-glass containing chloro- 

 form is floated on the surface of the water in which they are 

 contained, and the whole is covered with a bell-glass. As- 

 soon as the animals have become insensible, they are killed by 

 means of hot sublimate or chromic-acid solution plentifully 

 poured on to them. 



12. Liquid chloroform is employed by squirting it in small 

 quantities on to the surface of the water containing the 

 animals. A syringe or pipette having a very small orifice, so 

 as to thoroughly pulverise the chloroform, should be employed. 

 Small quantities only should be projected at a time, and the 

 dose should be repeated every five minutes, until the animals 

 are anaesthetised. 



