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THE POPULAR SCIENCE MONTHLY 



the most delicate, are made of horny matter, though it splits up into 

 so many shreds as it grows that they look like the finest hair, and Dr. 

 Gadow has reckoned that there must he fifty-four million branches and 

 threads upon one good-sized eagle's feather. 



From their skeletons and feathers which we find, we know that the 

 strange land-birds which perched on the trees at the time that large 

 reptiles were so numerous had not a fan-shaped tail, made of feath- 

 ers growing on one broad bone, as our birds have now, but they had 

 a long tail of many joints like lizards, only that each joint carried 

 a pair of feathers, and like lizards, too, they had teeth in their jaws, 

 which no living bird has. They must have been poor fliers at best, 

 these earliest known birds, for their wings were small and the fingers 

 of their hand were separate more like lizards' toes, two of them at 

 least having claws upon them, while their long, hanging tail must have 

 been very awkward compared to the fan-shaped tail they now wear. 



Our backboned animals have now traveled far along the journey 

 of life. The fish, in many and varied forms, have taken possession of 

 the seas, lakes, and rivers ; the amphibia fill the swamps and the de- 

 batable ground between earth and water ; the reptiles swarm in the 



