I893-] NEW-YORK MICROSCOPICAL SOCIETY. 37 



servative, is already covered with myriads of these destructive 

 agents, either mature or in the condition of gonidia, spores, or 

 eggs. In mounts from hands inexperienced in regard to this 

 danger, one can find, long after the preparation was made, an 

 abundance of living forms, particularly bacteria, which must be 

 preying upon the mounted object. To 'meet this attack some 

 suitable and permanent germicide should be added in proper 

 quantity as a constituent of the preservative. 



Mercuric chloride (corrosive sublimate), often used for this 

 purpose, should be avoided, in my opinion, on account of its un- 

 stable character, as it gradually loses chlorine and separates from 

 solution in the form of particles of calomel, feebly antiseptic if at 

 all; also on account of its corrosive nature, which tends to disin- 

 tegrate most forms of sarcode. 



Most acids, like carbolic (phenol and thymol), salicylic, picric, 

 boracic, arsenious, chromic, etc., are equally unsuitable, on account 

 of their corrosive nature and acid reaction. Camphor may be of 

 little permanent value, on account of its slight solubility in water 

 solution — ^•^., in the form of " camphor water " — and also its ready 

 absorption by organic matter of the walls of the mounting cells. 



As to chloral hydrate, there is increasing evidence as to its 

 possession of antiseptic power, as well as tendency to preserva- 

 tion of chlorophyll and coloring matters; while the satisfaction of 

 its affinity for water by a single molecule insures the absence of 

 farther dehydrating power. 



There are also several copper salts which seem to possess the 

 same desirable qualities as chloral, especially the chloride and 

 nitrate, and the principal objection to the acetate appears to be 

 its instability. 



In our own Laboratory experience, after trial of a large variety 

 of the preservatives in common use, we have found Petit^s solu- 

 tion apparently the most satisfactory for the preservation of fresh- 

 water algae and even colored fungi, with longest retention of both 

 form and color in the protoplasmic contents of their cells. This 

 conclusion is founded on an examination of several hundred 

 mounted preparations of these objects during a period of about 

 fifteen years past. The following is the well known modification ' 

 of Ripart's published formula : 



^ Internal. Jour. Micr. and Nat. Sci., 3 sen, ii. (1891), 177. 



