OCR Text |
Show 1891.] TADPOLES OF THE EUROPEAN BATRACHIANS. 599 pi. v. fig. 7), and in Pelodytes by Bedriaga (Bull. Soc. Nat. Mosc. 1889, p. 541). Their aspect is shown in the following figures, representing much-enlarged pieces of the upper caudal crest of Pelodytes and Discoglossus. Fig. 4. A B Much enlarged pieces of upper caudal crest of, A, Pelodytes punctatus, B, Discoglossus pictus. Preservation and Manipulation.-Tadpoles should be preserved in alcohol. Chromic acid is not to be recommended, as rendering the specimens too brittle for ordinary study. To ensure the good condition of specimens preserved in spirit, it is necessary to treat them with a little care ; tadpoles thrown into the ordinary collecting-bottle promiscuously with other specimens are never in a satisfactory condition for display in a collection and for future study. The best plan is to provide one's self, when going out collecting, with small test-tubes half-full of weak spirit; the tadpoles, when taken out of the fishing-net, should be dipped head foremost in the tube, which may be filled with as many specimens as it will hold. On reaching home, say two or three hours later, the liquor should be at once changed to strong spirit (40°), which will again require changing the next day, and so on until it ceases to be strongly coloured. By this method, of killing in weak spirit and then seizing by strong spirit, the tadpole preserves its natural shape in a remarkably perfect manner, and the delicate caudal crests do not shrivel. Specimens which have been only a few hours in spirit are in the best condition for study ; a slight pressure of the fingers on the back and breast causes the beak and lip to gape fully, showing the arrangement of the labial papillae and teeth. When studying specimens which have been a long time preserved, it is best to soak them for a few minutes in water, which, penetrating the subcutaneous vacuities, swells them out and restores their life-appearance. Tadpoles should never be allowed to remain out of the liquid, as they very rapidly shrink, especially the caudal crests. The lines of muciferous crypts are sometimes very difficult to trace. Heron Royer (Bull. Soc. Et. |