SOME METHODS FOR LOWER ANIMALS. 475 



wi*8. Mik., viii, 3, 1891, p. 363) found that a saturated 

 aqueous solution of cyanide of mercury, warmed to 45 to 

 50 C., and allowed to act for from fifteen m sixty minutes, 

 and then washed out with 70 per cent, alcohol, wsis the best 

 of all fixing media for Acanthocephali. 



He also found the following mixture excellent : 



Picric acid v, ... 1 gramme. 



Cone, sulphuric acid . . 10 gramim-. 



Chromic acid .... 1 gramme. 



Water . . 1000 grammes. 



To be warmed to 55 C., allowed to act for fifteen to 

 twenty minutes, washed out for five to ten minutes with 

 hot water, and afterwards for some days in 60 per cent, 

 alcohol. 



855. Nematodes. The extremely impermeable cuticle of 

 these animals is a great obstacle to preparation. According 

 to Looss (Zool. Anz., 1885, p. 318) this difficulty may be 

 overcome in the manner described in 556. 



For fixing, most recent authors recommend sublimate 

 solutions; chromic solutions seem to have a tendency to 

 make the worms brittle. 



But, according to ZUE STEASSEN (Zeit. f. u-iss. Zool., liv > 

 p. 655), Bradynema rigidum ought to be fixed for at least 

 twelve hours in mixture of Flemming. 



AUGSTEIN (Arch. f. Naturg. Jahrg., Ix, 1, 1894, p. 255 ; 

 Zeit. /. wiss. Mik., xii, 2, 1895, p. 227) found that for 

 Strongylus filaria the best fixing agent was Mayer's picro- 

 nitric acid. 



YEJDOVSKY (Zeit. wiss. Zool., Ivii, 1894, p. 645) advi>-< 

 for Gordius 0'5 per cent, chromic acid (twenty-four hours). 



Lo BIANCO (loc. cit., p. 462) employs for marine forma 

 concentrated sublimate or picro-sulphuric acid. 



COBB (ante, p. 4) uses his differentiator for bringing 

 through the various media after fixation. 



Staining is frequently difficult, and sometimes alcoholic 

 carmine, 229, is the only thing that will give fair result.-,. 



BBAUN (see Journ. Roy. Mic. Soc., 1885, p. 897) recommend* that small 

 unstained Nematodes be mounted in a mixture of 2t> parts gelatin, 100 

 parts glycerin, 120 parts water, and 2 parts carbolic acid, which is melted at 



