METHODS FOR INVERTEBRATES. 477 



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. 

 Central!;., vii, 1897, p. 321 ; and .as to that of the Grauula, 

 the same author, Zeit. 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. Site. 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, Jo-urn. Roy. Hie. 

 8oc., 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 1 . For killing by heat sec 13. 

 PFJTZNER (Morph. Jahrb., xi, 1885, p. 454) used concen- 

 trated solution of picric acid run in under the cover. 



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

 Kleinenberg to the water containing the organisms in a 

 uatcJi glass. 



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

 way 1 per cent, osmic acid, or, for Amoeba?, 2 per cent, 

 chromic acid. 



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

 recommends bringing tlic organisms into the fixing liquid with 

 a pipette. 



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

 see 83. 



For sulphurous acid, 62. 



CATTANEO (Bollettino Scicntifico, iii and iv Journ. Roy. 

 Mic. iSoc., 1885, p. 538) fixes for a few minutes with % per 

 cent, solution of chloride of palladium. 



BRASS (Zeit. -wi*s. Mik., 1884, p. 39) employs a mixture of 

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

 ncid with 400 to 1000 parts of water. 



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



