CILIATA 87 



vacuoles. The manner in which nutriment is taken up may be seen 

 by rubbing down a little powdered carmine in water and adding it to 

 the medium in which the organisms are examined, which should 

 not, in this instance, be thickened with carragheen. A good deal 

 is to be learnt from the living organism when stained with neutral 

 red. The arrangement of the cilia is an important factor in deter- 

 mining species. 1 



The Infusoria are best fixed with alcoholic solution of mercuric 

 chloride or with osmium vapour. In the latter case the material is 

 placed upon a cover-glass, which is held inverted over a vessel con- 

 taining osmic acid until the parasites turn brown. The cilia may now 

 be coloured with Schuberg's modification of Loffler's flagella stain. 

 The objects are immersed in a mordant mixture, consisting of 10 c.cm. 

 of a solution of 20 gr. tannin in 80 c.cm. distilled water, 5 c.cm. of a 

 saturated solution of ammonio-sulphate of protoxide of iron, and 

 1 c.cm. of a watery or alcoholic solution of wool-black. They are 

 put into a damp chamber for half an hour to one hour, and are after- 

 wards washed in water and absolute alcohol. They are stained 

 (half an hour to one hour) in a concentrated solution of fuchsin in 

 aniline water, to which a -f^ per cent, solution of soda has been added 

 in a quantity sufficient to start precipitation. Specimens must be 

 cleared in xylol, as oil of cloves will spoil the colour. They should on 

 no account be dried by the methods employed for bacteria ; the entire 

 process must be carried out wet, the different liquids being changed 

 by means of filter paper introduced between the cover-glass and the 

 slide. 2 



(a) Infusoria found in the Intestine of the Frog. 



Some of the most interesting of the parasitic Infusoria inhabit the 

 large intestine of the frog. The abdominal cavity of a freshly-killed 

 frog should be opened, and the short, k thick, terminal portion of the 

 intestinal canal should be freed and cut open. A small quantity of its 

 greenish contents is removed and diluted with a little normal saline. 

 As a rule, whitish, actively motile dots may be seen macroscopically, 

 and these will be most numerous upon that surface of the intestinal 

 contents which has been in contact with the intestinal wall. These 

 dots are Opalina. They are flat, disc-like Protozoa, and their entire 

 surface is covered with cilia, the movements of which resemble the 



1 F. Blochmann, " Die microscopische Tierwelt des Siisswassers," part i, 2nd ed., 

 Hamburg, 1895. 



2 A. Schuberg, "Ueber Cilien und Trichocysten einiger Infusorien," Arch. f. 

 Protistenkunde, vol. vi, 1905, part i, pp. 47-60. 



