Page:Popular Science Monthly Volume 15.djvu/382

 was their Balkan or Suleiman line, their cordon of border forts, their row of beacons to announce the approach of the hostile hill-men on the war-trail against their homes. Then our antiquary would turn to the work itself, and would point out the various parts, the mode of defense, the simple tactics of those primitive Vaubans. Or else he would show us the Roman detail of the later encampment; the square scar that marked the prætorian quarters; the regular succession of gates and defenses. All this he would tell us from the bare inspection of the existing remains, reconstructing the lost history from his stored-up knowledge of like instances elsewhere.

But I am wandering sadly from my London room and my little feather, this wintry afternoon. Let me look at it once more, and try to realize, in like manner, the story involved in its downy vans.

In the first place, this feather, as an anatomist would tell us, is "a dermal modification"—in other words, an altered bit of the skin. Every part of a plant or animal undergoes changes, our modern teachers say, just in accordance with the external influences which affect it. But the skin of an animal is naturally exposed to many more such surrounding agencies than its internal organs. Accordingly, we find that no structure exhibits such strange variations as the skin. Besides the regular modifications which we see in the scales or horny plates of fishes, the smooth coats or solid shells of reptiles, the feathers of birds, and the hair of mammals, numerous other minor peculiarities occur in almost every species. Such are the horns of cows and goats, the spike of the rhinoceros, the beaks, nails, claws, hoofs, and talons of beasts or birds, and the tail-plumes, ruffs, lappets, crests, and ornamental adjuncts of all the more aesthetic animals. In no class are these variations in the external covering more conspicuous than among the biped tribe whose spoils I am now holding in my hand as the text for our afternoon's discourse.

How birds first came to be winged and feathered we can hardly say as yet. To be sure, most of us have seen a picture, at least, of that strange oolitic monster, the pterodactyl, a saurian with a head like a crow, but having the fore-part protracted into long jaws, fitted with teeth not very dissimilar from those of a crocodile; while its legs were supplied, apparently, with a membrane, by whose aid the creature probably flew about in the same manner as a bat. These real flying dragons recall in many points the appearance of a bird, especially in the skull and the position of the eyes. Moreover, Professors Marsh and Huxley have shown that the earliest fossil birds resemble the pterodactyl and other reptiles in many important peculiarities of structure, far more than their modern representatives. Some of them even possess teeth set in their jaws after a reptilian fashion. Though the evidence still remains very fragmentary, we may regard it as probable that birds are descended from some early reptilian form, more or less like the peterodactylpterodactyl [sic], if not actually from that partially-winged saurian