SOME METHODS FOR LOWEE ANIMALS. 473 



a thin film on to the surface of the water. After four to eight 

 hours, if the animals make 110 contractions on being stimu- 

 lated, they may be removed to 50 per cent, alcohol. 



S. Lo BIANCO says killing with 0*5 per cent, chromic acid 

 or with Ol per cent, chloral hydrate in sea water may be 

 tried, but either method is uncertain. Phascolosoma and 

 Phoronis should be treated by the alcohol method. 



APEL (Zeit. f. iviss. ZooL, xlii, 1885, p. 461) says that 

 Priapulus and Halicryptus can only be satisfactorily killed by 

 heat. The animals may either be put into a vessel with sea 

 water and be heated on a water-bath to 40 C.; or they may 

 be thrown as rapidly as possible into boiling water, which 

 paralyses them so that they can be quickly cut open and 

 thrown into -^ per cent, chromic acid or picro-sulphuric acid. 



853. Rotatoria. By far the most important method for the 

 study of this group consists in the observation of the living 

 animals. For quieting them WEBER (Arch. Je Biol., viii, 4, 

 1888, p. 71o) finds that of all the reagents he tried, 2 per 

 cent, solution of hydrochlorate of cocaine gave the best 

 results. Warm water gave him good results for large 

 species, such as those of Hydatina and Brachionus. 



HARDY (Journ. Roy. Mic. Soc., 1889, p. 475) recommends 

 thick syrup added drop by drop to the water. HUDSON (ibid., 

 p. 476) mentions weak solution of salicylic acid. 



HOFER'S hydroxylamin method has been given, 20, and 

 TULLBERG'S chloride of magnesium method, 21 ; the pro- 

 cesses of EISMOND and JENSEN, 879, maybe tried. Methy- 

 len blue, 323, may be found useful. 



Permanent preparations may be made by the method of 

 ROUSSELET (Journ. Qnekett Mic. Club, v, March, 1895, p. 1) : 

 The animals are got together in a watch glass and are 

 narcotised by adding to the water at intervals a few drops 

 of the following mixture : 



Hydrochlorate of cocaine 2 per cent, solution . 3 parts. 

 Methyhited spirit . . . .1 part. 



Water . . . . .6 parts. 



They are watched under a dissecting microscope, and at 

 the moment when the cilia have ceased to beat, or are seen 

 to be on the point of ceasing to beat, they are fixed by 

 adding a drop of liquid of Flemming or of per cent osmic 



