1893.J MICROSC^OPICAL JOURNAL. 275 



up; hut tliose in glyccriiu' were as perfect as ever. The enor- 

 mous expense of the process I overcame hy fillinfr up the bottles 

 with lead vessels painted white. This saved <^lyeerine; hut the 

 gum was also costly. Then the fish were dehydrated in spirit, 

 so that the gum and glycerine could be used over and over 

 again. Only very scaly fish, such as sea perches and wrasse?*, 

 and a few echinoderras, can be jirepared in this way. Ordinary 

 fish, snakes, and frogs are withered up by it out of all recogni- 

 tion, and rendered as hard as iron. Was there any possibility 

 of rendering tlie specific gravity of the gum and glycerine less ? 

 I devoted myself to this for a long time. No additions of wat- 

 ery solutions of any substances were of avail. At last I found 

 that by gently mixing with weak spirit, briskly stirring all the 

 time, that the gum, at first precipitated in fiocculent masses, 

 was re-dissolved, and that in that way solutions of almost any 

 specific gravity could be ol)tained. But it is only very small 

 specimens that can be mounted in this way, the medium being 

 too opaque for any larger bottles, nor is it a good mounting me- 

 dium even for them. 



If we attempt to mount s{)ecimen8 jjreserved in this way in 

 pure glycerine, they are shrivelled up almost as badly as if pre- 

 served with the full strength of the gum and glycerine mixture. 

 Many attempts were made to reduce the specific gravity of the 

 glycerine. Why not try spirit ? Glycerine and spirit are most 

 powerful preservatives, and have the inestimable advantage in 

 this hot climate of not evaporating, but they are absolutely de- 

 structive to all color, bleaching the specimens with great rapid- 

 ity. If watery solutions of salts or acids are used to reduce the 

 specific gravity, a grand crop of fungus springs up at once. The 

 only successful chemical was chloral, but it was soon found that 

 light colors faded in watery solutions almost as soon as in alco- 

 holic preparations. 



My next experiments were solutions of gelatine in spirit. 

 This is a very good preservative, but it does not keep bright 

 color. There is, perhaps, nothing better for frogs, all the deli- 

 cate folds and glandular lines so important in identifying the 

 species of this very difficult class of animals being preserved as 

 in life. The mixture is made by soaking a packet of Nelson's 

 gelatine in a pint of cold water for ten or twenty minutes 

 which is sufficient in this climate. Dissolving it by a gentle* 



