Darwin found a curious little toad, the Phryniscus nigricans, on the dry sandy soil of the Pampas, "which looked," he says, "as if it had been steeped in the blackest ink, and then, when dry, allowed to crawl over a board freshly painted with the brightest vermilion." Instead of being nocturnal in its habits, as other toads are, and living in obscure recesses, it crawls about over dry hillocks and arid plains during the day, where not a single drop of water can be found. It depends on the dew for its moisture, which is probably absorbed by the skin. The creature seems to dread water, and is utterly unable to swim. THE SURINAM TOAD. The Surinam toad is one of the most curious, though, at the same time, among the most hideous of batrachians. It is remarkable on account of the extraordinary way in which its young are developed. The skin of the female is separated, as is the case with others of its family, from the muscles of the back, and is nearly half an inch thick. She deposits her eggs, or spawn, at the brink of some stagnant water, when the male manages to take them up in his paws and places them on her back, where they adhere by means of a glutinous secretion, and are pressed into cells which, at that time, are open to receive them. Gradually the cells are closed by a membrane which grows over them, when her back greatly resembles a piece of honeycomb, the cells of which are filled and closed. Here, in the course of about three months, the eggs are hatched, and the creatures undergo the usual change of the rest of the genus; first assuming the form of tadpoles, and gradually acquiring their complete shape. When perfected, and possessed of their limbs, they work their way out of the cells; and it is a curious sight to see them struggling out--their head and paws projecting in all directions from their mother's back--and sliding down on the ground, when they begin to hop merrily about. The cells are considerably deeper than wide, and each would contain an ordinary bean thrust endwise into it. The head of the creature is of an unusual shape, as it has a snout with nostrils lengthened into a kind of tube. The skin is of a brownish-olive above, and white below; and is covered with a number of small, hard granules, with some horny tubercular projections among them. After the brood have left the mother's back, the cells again fill up--the whole process occupying about eight days. In spite of the repulsive appearance of the creature, the negroes occasionally eat it. TORTOISES. Tortoises (Testudinata, or Chelonians) belong to a very numerous order of reptiles, the usual form of which is too well known to require description. They are shut up, as it were, in a box and breast-plate: the carapace and plastron, in reality, are external developments of certain parts of the skeleton.