tentative variations in the stiffness of the web material must there have been before the precise degree was attained enabling the two distinct species, differing in colour, to complete their resemblance to falling leaves--a fresh green leaf in one case and a dead, withered leaf in the other! The Tetragnatha--a genus of the Epeira family, and known also in England--are small spiders found on the margin of streams. Their bodies are slender, oblong, and resembling a canoe in shape; and when they sit lengthwise on a stem or blade of grass, their long, hair-like legs arranged straight before and behind them, it is difficult to detect them, so closely do they resemble a discoloured stripe on the herbage. A species of Tetragnatha with a curious modification of structure abounds on the pampas. The long leg of this spider is no thicker than a bristle from a pig's back, but at the extremity it is flattened and broad, giving it a striking resemblance to an oar. These spiders are only found in herbage overhanging the borders of streams: they are very numerous, and, having a pugnacious temper, are incessantly quarrelling; and it frequently happens that in these encounters, or where they are pursuing each other through the leaves, they drop into the water below. I believe, in fact, that they often drop themselves purposely into it as the readiest means of escape when hard pressed. When this happens, the advantage of the modified structure of the legs is seen. The fallen spider, sitting boat-like on the surface, throws out its long legs, and, dipping the broad ends into the water, literally rows itself rapidly to land. The gossamer-spider, most spiritual of living things, of which there are numerous species, some extremely beautiful in colouring and markings, is the most numerous of our spiders. Only when the declining sun flings a broad track of shiny silver light on the plain does one get some faint conception of the unnumbered millions of these buoyant little creatures busy weaving their gauzy veil over the earth and floating unseen, like an ethereal vital dust, in the atmosphere. This spider carries within its diminutive abdomen a secret which will possibly serve to vex subtle intellects for a long time to come; for it is hard to believe that merely by mechanical force, even aided by currents of air, a creature half as big as a barley grain can instantaneously snoot out filaments twenty or thirty inches long, and by means of which it floats itself in the air.