METHODS FOB QUIETING INFUSORIA. 461 



hanging-drop moist chambers, oxygenated by means of a few 

 fronds of green algae. He also (ibid., xxxiv, 1880, p. 416) 

 found that the best sections of the more advanced sessile larvae 

 of Plakina were obtained by selecting larvae that had settled 

 down on thin fronds of algae, and treating them, together with 

 the fronds, with osmic acid, staining with alum-carmine, and. 

 bringing into paraffin in the usual way. 



Protozoa. 



857. Introductory. Since the Protozoa may be considered 

 as free cells, and their peculiar organs known as "nucleus" 

 and " nucleolus," " macronucleus " and " micronucleus," &c., 

 present in the main the same reactions as cell-nuclei, it is 

 evident that the reagents and methods of cytology are in great 

 part applicable to this group. One of the most generally 

 useful of these reagents will be found in the acid solution of 

 methyl green; it is the reagent that allows of the readiest and 

 best demonstration of the presence and form of the nucleus 

 and nucleolus (BALBIANI et HENNEGUY, Compt. rend. Soc. de 

 BioL, 1881, p. 131). The EHELICH-BIONDI mixture, 259, will 

 of course in many cases be indicated. 



Amongst useful reagents not mentioned in the following 

 descriptions of the methods employed by different authors, I 

 call attention to the weak solutions of alum, potash, and borax, 

 which serve to demonstrate the striations of the cuticle and 

 the insertions of the cilia of Infusoria. 



858. Methods for quieting Infusoria. The narcotisation 

 methods, 14 to 18, are available for this purpose, as is also 

 the monobromated camphor process of BROCHEE, 811, which 

 I believe has been found very successful with Yorticellidae. 



According to SCHURMAYER (Jen. Zeit., xxiv, 1890, pp.402 

 470; Zeit. f. wiss. Mik,, vii, 4, 1891, p. 493) nitrate of strychnin 

 in weak solution, O'Ol per cent, or less, gives good results with 

 some forms, amongst which are Stentor and Carchesium. 

 Antipyrin in concentrated solution (O'l per cent.) or cocain of 

 O'Ol per cent, seems only to have given good results as regards 

 the extension of the stalk in stalked forms. 



EISMOND (Zool. Anz. y No. 352, Dec., 1890, p. 723) has 

 proposed a mechanical means of slowing the movements of 

 small organisms (small worms and Crustacea as well as 



