The subject is interminable, but we must give a passing glance to some quixotic tails. The opossum scampers up a tree, carrying all her numerous family on her back, and they do not fall off because each infant is securely moored by its own tail to the uplifted tail of its mother. The opossum is a very primitive beast, and so early and useful an invention should, one would think, have been spread widely in after time; but there appears to be some difficulty in developing muscles at the thin end of a long tail, for the animals that have turned it into a grasping organ are few and are widely scattered. Examples are the chameleon among lizards, our own little harvest mouse, and, pre-eminent above all, the American monkeys. To a howler, or spider-monkey, its long tail is a swing and a trapeze in its forest gymnasium. Humboldt saw (he says it) a cluster of them all hanging from a tree by one tail, which proceeded from a Sandow in the middle. I should like to see that too. It is worth noting, by the way, that no old-world monkey has attained to this application of its tail. Then there is the beaver, whose tail I am convinced is a trowel. I know of no naturalist who has mentioned this, but such negative evidence is of little weight. The beaver, as everybody knows, is a builder, who cuts down trees and piles log upon log until he has raised a solid, domed cabin from seven to twenty feet in diameter, which he then plasters over with clay and straw. If he does not turn round and beat the work smooth with his tail, then I require to know for what purpose he carries that broad, heavy, and hard tool behind him. How few even among lovers of Nature know why a frog has no tail! The reason-is simply that it used that organ up when it was in want. In early life, as a jolly tadpole, it had a flourishing tail to swim with, and gills for breathing water, and an infantile mouth for taking vegetable nourishment. But when it began to draw near to frog's estate, serious changes were required in its structure to fit it for the life of a land animal. Four tiny legs appeared from under its skin, the gills gave place to air-breathing lungs, and the infant lips to a great, gaping mouth. Now, during this "temporary alteration of the premises" all business was of necessity stopped. The half-fish, half-frog could neither sup like an infant nor eat like a man. In this extremity it fed on its own tail--absorbed it as a camel is said to absorb its hump when travelling in the foodless desert--and so it entered on its new life without one.