448 SOME ZOOLOGICAL METHODS. 



four to eight hours, if the animals make no contractions on 

 being stimulated, they may be removed to 50 per cent, 

 alcohol. 



S. Lo BIANCO says killing with O5 per cent, chromic acid 

 or with O'l 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. wiss. 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 possibly into boiling water, which 

 paralyses them so that they can be quickly cut open and 

 thrown into one third per cent, chromic acid, or picro- 

 sulphuric acid. 



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

 study of this group consists in the observation of the living 

 animals. Great difficulty exists in the way of getting them 

 to keep sufficiently quiet. VOGT and YUNG (Anat. comp. prat., 

 p. 420) say that a drop of solution of any of the soluble salts 

 of strychnin run under the cover sometimes renders service. 

 WEBER (Arch, de Biol., viii, 4, 1888, p. 713) finds that 

 strychnin, prussic acid, and curare act too strongly; of all 

 the reagents he tried, 2 per cent, solution of hydrochlorate of 

 cocain gave the best results. Warm water gave him good 

 results for large species, such as those of Hydatina and 

 Brachionus. 



HARDY (Journ. Roy. Hie. 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, 16, and 

 TULLBERG'S chloride of magnesium method, 17. BROCHER'S 

 monobromated camphor, 811, should be tried; as should 

 also the processes of EISMOND and of JANSEN, 858. Methylen 

 blue, 114, may be found useful. 



Permanent preservation of Rotifers has hitherto been 

 considered by those who have tried it to be well-nigh impos- 

 sible. ROUSSELET (Journ. Quek. Mic. Club, v, 2, 1893, p. 205; 

 Journ. Roy. Mic. Soc., 1893, p. 262) has, however, lately had 

 a considerable measure of success. The animals should be 



