MOUNTING MEDIA. 69 



the cover-glass), has been recommended. There 

 are, however, so many unpleasant features about 

 the use of this preservative that I prefer not to 

 use it. 



ACETATE OF POTASSIUM. A concentrated aque- 

 ous solution is used for preparing algae for ana- 

 tomical preparations as well as for the preservation 

 of bacteria stained in methyl-violet. Slides should 

 lie twenty-four hours before the covers are sealed 

 down. 



[MONOBROMO-NAPHTHALIN is employed by Moller 

 in mounting diatoms for test objects, because of 

 its great refractive power. The markings of the 

 frustules come out nearly as well as in dry mounts, 

 while the specimens present a much better appear- 

 ance.' 



PHOSPHORUS is also used for the same class of 

 objects, giving, it is said, even better results. 

 W. T.] 



CANADA BALSAM, which liquefies when slightly 

 warmed, is much used in mounting diatoms, the 

 fine structure of their frustules being brought out 

 very clearly by it. Instead of the pure balsam, a 

 concentrated solution in ether or chloroform, which 

 is far cleanlier, may be used. 



[For most purposes benzole-balsam is, by some, 

 preferred to either of these solutions. It is pre- 

 pared by exposing commercial "balsam of firs" to 

 gentle heat in a shallow dish, loosely covered to 



1 Cf. Journ. Roy. Micr. Soc., 1880, III., p. 1043. 



