XI.-On a Method of Preserving the Fresh-water Medusa
Journal of the Royal Microscopical Society
THE freshwater Medusa (Linanocodium Sowerbii) found in the Victoria Regia tank at the Botanic Gardens, Regent'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 things were tried, but in no case was the result wholly satisfactory.
... lly satisfactory. Before giving the matter FIG. 90. &%&t swz.kn&g& 2Xe W L J i r & aL ±* M. up, I thought well over the structure of the animal, and its probable 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 ox. of distilled water). The result fully answered my expectations, and the animals were completely preserved, and in a form which malies them more easy of examination than when living. 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