18 CHAPTER II. 



Narcotisation is very rapidly obtained with very small 

 animals, but much more slowly with larger ones. For 

 instance,, Stylaria proboscidea, I find, is paralysed in a few 

 seconds ; a small Nephelis, of 15 or 20 millimetres in length,, 

 will require about five minutes ; and a large Nephelis, of 

 from 10 to 15 centimetres, will require as many hours. Nar- 

 cotised animals recover very quickly on being put back into 

 pure water. 



UEXKULL (Mitth. Zool. Stat. Neapel, xii, 1896, p. 463) has 

 paralysed Echinids very rapidly with carbonic acid, likewise 

 a small Teleostean fish; whilst Scy Ilium and Crustaceans 

 were affected much more slowly, and mussels not at all. 



25. Peroxide of Hydrogen. VOLK (Zool. Anz., Bd. xix, 1896, 

 p. 294) kills Rotatoria by means of one or two drops of a 

 3 per cent, solution added to 1 c.c. of the water containing 

 them. If the right dose has been hit off they die extended,, 

 and are then brought first into pure water and then into 

 some fixing liquid. 



