492 CHAPTER XXXIV. 



880. Staining intra vitam. The possibility of staining In- 

 fusoria intra vitam was discovered independently by BRANDT 

 (Verh. d. physiol, Ges. Berlin, 1878), by CEETES (Bull. Soc. 

 ZooL, 25 janv., 1881), and by HENNEGUY (Soc. Philom., 12 

 fev., 1881). See on this subject 201. 



BRANDT recommends a 1 : 3000 solution of Bismarck brown; 

 also (Biol. CentralbL, i, 1881, p. 202) " a dilute solution of 

 heematoxylin." 



CERTES (op. cit., pp. 21, 226, 264, and Zool. Anz., iv, 1881, 

 pp. 208, 287) found that living Infusoria stain in weak solu- 

 tions of cyanin, Bismarck brown, dahlia, violet 5 B, chrysoidin, 

 nigrosin, methylen blue, malachite green, iodine green, and 

 other tar colours, and hasmatoxylin. The solutions should be 

 made with the liquid that constitutes the natural habitat of 

 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. 

 'CentralbL, vii, 1897, p. 321 ; and as to that of the Gramila, 

 the same author, Zeit. f. iciss. Mik., xiii, 1896, p. 478. 



Examination in a coloured medium in which the organisms 

 do not stain, but show up on a coloured background in a 

 manner that produces somewhat the effect of dark-ground 

 illumination, is sometimes helpful. CERTES (Bull. Soc. Zool. 

 de France, xiii, 1888, p. 230) recommends solution of anilin 

 black for this purpose ; Infusoria will live in it for weeks. 

 FABRE-DOMEKGUE (Ann. de Microgr., ii, 1889, p. 545; Jo urn. 

 Roy. Mi<>. Soc., 1889, p. 832) recommends concentrated solu- 

 tion of diphenylamin blue. 



881. Fixing and Preserving. For killing by heat see 11, 

 p. 12. 



IViTZXHK (Mvrjili. Jahrb., xi, 1885, p. 454) used concen- 

 trated solution of picric acid run in under the cover. 



BLANC (Zool. An?.., vi, 1882, p. 22) advises liquid of Kleinen- 

 berg diluted with about a volume of water, and acidified with 

 acetic- acid. 



GE/.A KNT/ (ibid., iv, 1881, p. 575) adds it to the water 

 containing the organisms in a ((.atch-ylass. 



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



