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XI. — On a Method of F reserving the Fresh-water Medusa, 

 By Petek Squike, F.L.S. 



^Received 9th July, 1883.) 



The freshwater Medusa (Limnoeodium Sowerhii) found in the 

 Victoria Eegia tank at the Botanic Gardens, Kegent's Park, is a 

 singularly beautiful object (see fig. 90). As I learnt from Mr. 

 Sowerby that all attempts to preserve it for future observation had 

 failed, I was induced to make some experiments in this direction. 

 Various antiseptic media, such as Goadby's solution, and solutions 

 of glycerine, kreosote, and many other thiags were tried, but in no 

 case was the result wholly satisfactory. Before giviug the matter 



Fig. 90. 



up, I thought well over the structure of the animal, and its prob- 

 able chemical constitution, and it occurred to me that, if albumen 

 was chiefly concerned, bichloride of mercury would render it 

 opalescent and less liable to change. Accordingly I plunged the 

 creatures into very dilute solutions of this reagent (2 grains only in 

 a pint of 20 oz. of distilled water). The result fully answered my 

 expectations, and the animals were completely preserved, and in a 

 form which makes them more easy of examination than when Hving. 

 Their bodies being rendered opalescent, the minutest details become 

 apparent, while during life the animals are so transparent as to be 

 scarcely visible. In order to guard against failure I have since 

 increased the strength of the solution to 4 grains in the pint. 



To obtain good results several precautions are necessary. As 

 the animals live in water at a temperature of 85° F. it will not do 

 to plunge them into a cold solution of bichloride, nor into a strong 

 solution even if warm. In either case the animals appear to sustain a 

 shock. They shrivel up at once, and the specimens thus preserved 

 have little resemblance to the living creatures. The solution must 

 be previously raised to the temperature of 85° F., and its strength 

 must not exceed 4 grains to the pint. The animals are best conveyed 

 into it by means of a glass tube acting as a pipette. Under these 



