METHODS FOK INVKKTEHKATKS. 177 



the organisms. They should be very weak, that is of 

 strengths varying between 1 : 10,000 and 1 : 100,000. For 

 cyanin, 1 : 500,000 is strong enough. 



As to the staining of the Nucleus, see PRZESMYCKI, BioL 

 Centrnlb., vii, 1897, p. 321 ; and as to that of the Granula, 

 the same author, Zeif. wiss. Mik., xiii, 1896, p. 478. Also 

 LOISEL, 208, 



Examination in a coloured medium in which the organisms 

 do not stain, but show up on a coloured background is some- 

 times helpful. CERTES (Bull. S<>c. Zool. de France, xiii, 1888, 

 p. 230) recommends solution of anilin black Infusoria will 

 live in it for weeks ; FABRE-DOMERGUE ( Ann. de Microgr., ii, 

 1889, p. 545) concentrated solution of diphenylamin blue. 



919. Demonstration of Cilia (WADDINGTON, Journ. Roy. Mic. 

 Soc.j 1883, p. 185). A drop of solution of tannin, or a trace 

 of alcoholic solution of sulphurous acid, added to the water 

 containing the living organisms. 



920. Fixing and Preserving. For killing by heat see 13. 

 PFITZNER (Morplt. Jahrb., xi, 1885, p. 454) used concen- 

 trated solution of picric acid run in under the cover. 



ENTZ (Zool. Anz., iv, 1881, p. 575) adds liquid of 

 Kleinenberg to the water containing the organisms in a 

 irate It gla*$. 



KOKSCHELT (ibid., v, 1882, p. 217) employs in the same 

 way 1 per cent, osmic acid, or, for Amoeba3, 2 per cent, 

 chromic acid. 



LANSBERG (ibid., p. 336) advises the same reagents, but 

 recommends bringing the organisms into the fsring liquid with 

 a pipette. 



For fixation with iodine (KENT) or iodine vapour (OVERTON), 

 see 83. 



For sulphurous acid, 62. 



CATTANEO (Bollettino Scientific^ f iii and iv ; Journ. Roy. 

 Mic. Soc., 1885, p. 538) fixes for a few minutes with ^ per 

 cent, solution of chloride of palladium. 



BRASS (Zcit. -wiss. Milt., 1884, p. 39) employs a mixture of 

 1 part each of chromic acid, platinum chloride, and acetic 

 acid with 400 to 1000 parts of water. 



CERTES (Comptes rend., Ixxxviii, 1879, p. 433) fixes with 



