"As regards the internal shell, it may be obtained by making a conical incision in the shield, taking care not to cut down upon the calcareous plate, which can then be removed without difficulty. The animals can only be conserved by keeping them in some preservative fluid; but the great object to keep in view is to have the slug naturally extended. Most fluids contract the slugs when they are immersed in them. The slugs should be killed whilst crawling, by plunging them into a solution of corrosive sublimate, or into benzine. Models in wax or dough are sometimes substituted for the animals. A writer in the 'Naturalist' gives a process for the preservation of slugs, which he states to answer admirably, and to be very superior to spirit, glycerine, creosote, and other solutions:—'Make a cold saturated solution of corrosive sublimate; put it into a deep wide-mouthed bottle; then take the slug you wish to preserve, and let it crawl upon a long slip of card. When the tentacles are fully extended, plunge it suddenly into the solution; in a few minutes it will die, with the tentacles fully extended in the most life-like manner; so much so indeed, if taken out of the fluid it would be difficult to say whether it be alive or dead. The slugs thus prepared should not be mounted in spirit, as it is apt to contract and discolour them. A mixture of one and a half parts of water and one part of glycerine, I find to be the best mounting fluid. It preserves the colour beautifully, and its antiseptic qualities are unexceptionable. A good-sized test-tube answers better than a bottle for putting them up, as it admits of closer examination of the animal. The only drawback to this process is, that unless the solution is of sufficient strength, and unless the tentacles are extruded when the animal is immersed, it generally, but not invariably, fails. Some slugs appear to be more susceptible to the action of the fluid than others; and it generally answers better with full-grown than with young specimens. But if successful, the specimens are as satisfactory as could be desired; and even if unsuccessful, they are a great deal better than those preserved in spirit; for, although the tentacles may not be completely extruded, they are more or less so'".
The Testacellæ I have treated in the following manner: by partially drying them in sand, and removal of the soft parts through a cut in the length of the foot, filling up with cotton wool and a renewal of the drying.
Our land and freshwater snails have other structures besides their shells which should claim our attention. These, which include their jaws, tongues, and some other minute parts, are not so inaccessible as one is at first too apt to consider, and are deservedly in favour as microscopic objects requiring a low power. I shall assume that the collector has preserved the bodies or the heads of the snails in spirit, which he has removed from their shells in the process of preparing them for his cabinet. He will take care to keep separate the animals of each species.
A last word upon the mode of displaying the shells in the cabinet. Here one has considerable choice, as they may be kept in open card trays, or in glass-topped boxes, or gummed on cards, papered boards, or glass tablets. Loose specimens admit of ready examination, whilst the method of mounting permits an arrangement of individuals according to size and locality, and is much to be preferred.
VIII.
FLOWERING PLANTS AND FERNS.
By James Britten, F.L.S.
PART I.