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Show 160 MR. TEGETMEIER ON SIREDON MEXICANUS. [Mar. 24, situation so badly adapted for its structure and habits? But, in truth, natural selection has done absolutely nothing for our Woodpecker. Its colours are not dimmed, nor its loud notes subdued; but even when it traverses the open country it calls about it the enemies from which it has little chance to escape. Natural selection has not endowed it, for its safety, with the instinct of concealment, so common in the true pampas birds. Its peculiar flight also, so admirably adapted for gliding through the forest, here only excites the rapacious birds to pursuit. In fact, the residence of this species in a region of which the conditions seem inimical to its preservation, so far from modifying, seems rather to have intensified its characteristics. Compared with the other Woodpeckers of this portion of South America, in structure, size, colour, voice, and flight, it is the type of the genus. The habit of occasionally perching on the ground it possesses in common with other species; but it never roosts on the ground, like the true pampas birds ; never builds a nest or burrows in banks, like the Patagonian Parrot; nor ventures on to those vast and treeless plains that border on its habitat. Scarcity of provisions and seeking for trees better adapted for breeding, with, perhaps, other reasons, have probably led to the distribution of this species over a great extent of country. " Twenty years ago, which is as far back as m y recollection extends, the Carpintero was rather a common bird ; but it has now become so very rare, that for the last four years I have met with only three individuals." Mr. Tegetmeier exhibited living specimens of the Axolotl (Siredon mexicanus), one of which (fig. 1, p. 161) had undergone the metamorphosis described by M . Aug. Dumeril in the 'Annales des Sciences Naturelles' for 1867. This animal had hitherto been regarded as a perennibranchiate amphibian, as it breeds freely in the larval state, and in Mexico appears to be only known in that condition, although many naturalists have suspected it to be the larva of a large Salamander. The specimens exhibited were hatched in the summer of 1868, aud kept under similar conditions, without any change taking place beyond a steady increase of growth, during the succeeding winter and summer of 1869. In the autumn one only out of five began to change ; the external gills disappeared, the jaws became much more pointed, and the skin assumed a singularly mottled appearance. The animal did not leave the water, but, when the temperature was warm, usually breathed by standing erect against the side of the aquarium and elevating the nostrils above the surface, respiration being effected by the very rapid movement of the skin of the lower jaw. During cold weather it usually remained submerged, rising at intervals to the surface to breathe. Mr. Tegetmeier also exhibited some microscopic slides, on which were mounted portions of the excessively thin cuticle of the feet of the animals, that had been shed like a glove, the skin of the toes being partly inverted, |
