The arrangement of the long hairs, projecting out sidewise on the bone, is strikingly like that of the feathers on the tail of the very earliest reptile-like birds which had long bony tails, used doubtless as the squirrel's, since they were down-sailers rather than up-flutterers--if I may be allowed to so compound my words and ideas. Some other downward-leaping mammals have the hairs similarly arranged. Another rodent, the anomalure, which flies down, as a flying-squirrel, by thin membranes, has special horny scales on the under side of its tail either to assist in climbing or to resist slipping down when a tree trunk is grasped. The squirrel's tail, therefore, is a factor of his safety, as well as a feature of his ornamentation. Another use which he makes of it is that when he "lies down to pleasant dreams" it forms "the drapery of his couch"--a coverlid for his head and body. [Illustration: FROM COL. CHI. ACAD. SCIENCES. NORTHERN HARE. 1/3 Life-size. COPYRIGHT 1899, NATURE STUDY PUB. CO., CHICAGO.] THE NORTHERN PRAIRIE HARE. This is the most northern species of the group of hares (_Lepus campestris_), familiarly known in the United States as jack rabbits because of their large size and enormous ears. They are lively animals of astounding jumping powers. In America there is no such distinction between the term "hare" and "rabbit" as there is in Europe, where the large, long-eared, stout varieties, living in shallow "forms," are named hares, and the smaller and more slender kind, which digs a deep burrow, is the "rabbit." In this country the authorities say that no well-defined distinction exists. Of the so-called jack rabbits the northern prairie hare here depicted may be taken as the type. It is one of the largest species of hares, measuring about twenty inches in length, and it has long, strong, and vigorous limbs, and such remarkably long ears that the popular name it bears is fully justified. This northern species is found on the western prairies from British America to Colorado. It undergoes a winter change of coat, becoming nearly white, but the blanching is never complete and russet streaks or patches remain through the winter. The habits of this animal are those of hares in general, and all the species known as jack rabbits are famous for their great speed and for the astounding leaps they make in running. They are the most fleet and agile of American mammals. They are not much pursued for the reason that they are difficult to shoot, and their celerity of movement enables them to elude four-footed foes also. Pending the complete change from the summer brown to the snowy-white coat of winter, the animal presents a very singular mottled appearance.