492 JOURNAL,, BOMBAY NATURAL HISTORY SOCIETY, 1891. 



powerful preservatives, and have the inestimable advantage in this hot climate 

 of not evaporating or at least not perceptibly, bnt they are absolutely destruc- 

 tive to all colour, bleaching the specimens with great rapidity. If watery solu- 

 tions of salts or acids were used to reduce the specific gravity a grand crop of 

 fungus sprung up at once. The only successful chemical was chloral, but it was 

 soon found that light colours faded in watery solutions, almost as soon as in 

 alcoholic preparations. E is an example of a chloralized glycerine solution of 

 about the specific gravity of milk, three years old ; but it is expensive, and has 

 no particular advantage, except that it does not evaporate. My next experi- 

 ments were solutions of gelatine in spirit. It is a very good preservative ; but 

 it does not keep colour. There is, perhaps, nothing better for frogs, all the 

 delicate 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 10 or 20 

 minutes, which is sufficient in this climate. After dissolving it by a gentle heat, 

 it is carefully stirred up with sufficient cold proof spirit ; the mixture should 

 measure about 40 degrees below proof. F is a specimen of a very young exam- 

 ple of a very rare species of frog, prepared in this medium, and mounted in 

 chloralized glycerine. G is another example of a moderately sized frog, mounted 

 in weak spirit, which is a better mounting medium. We have now two pro- 

 cesses, one a splendid colour preserver of very limited use, the other an excellent 

 preservative for very delicate objects, but not a preserver of any bright colours, 

 although for dark tints it does very well. I now come to a very difficult 

 subject— What is the action of the gum and glycerine ? I have long thought 

 and even reported in one of my administration reports, that the gum was the 

 colour preserver, and that the glycerine acted first by dehydrating the animal, 

 and then by excluding air and water. I was led to this conclusion by the fact 

 that the addition of water destroyed the colours, as I imagined, by again 

 extracting the gum from the tissues. But I am now convinced this is not 

 the case ; the action of the gum is to harden the tissues against the 

 softening influence of the glycerine ; the real colour preserver is the glycerine, 

 and it preserves because it excludes air and water. Amongst some fish 

 presented a great many years ago by Mr. Bell, was a specimen of a red 

 sea perch (specimen H) in arrack, which had a bit of its bright red colour 

 left where it was tightly pressed against the glass. This specimen had 

 always had a great fascination for me, as it is a species in which the colour fades 

 in a few hours. The idea of finding some process by which animals would be 

 shut up in some kind of solid led me to try hardened Canada balsam. J, a tely- 

 phonus, mounted in a solid glass made by evaporating Canada balsam to dry- 

 ness and then re-melting it, and pouring itover the animal. The heat, however, 

 is too great to make it an available process, and the exhibited specimen is the 

 only success I ever obtained. It was prepared in 18S3. Now, the fact is the 

 glycerine, by excluding air and water, does act as a solid glass, and the only 



