3 68 THE POPULAR SCIENCE MONTHLY. 



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 praetorian 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 teach- 

 ers say, just in accordance with the external influences which affect it. 

 But the skin of an animal is naturally exposed to many more such sur- 

 rounding 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 after- 

 noon'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 struc- 

 ture, 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 peterodactyl, if not actually from that partially-winged saurian 



