. Bird-life . ust rest. To bring outthe full significance of this we will enlarge uponour remarks in chapter IV., and endeavour toshow, by comparison, how the wings of thepterodactyle, the bat, and the bird, are allmodifications of one common type — a five-fingered hand. In the wings of all these it is the fingers, ormore exactly the hand, which have undergonethe greatest changes in this transformation intothe wing. In the pterodactyle all five fingers are re-tained. The first four, however, are greatlyreduced in size. Three of them are providedwith small claws, and probably served to sus-pend
. Bird-life . ust rest. To bring outthe full significance of this we will enlarge uponour remarks in chapter IV., and endeavour toshow, by comparison, how the wings of thepterodactyle, the bat, and the bird, are allmodifications of one common type — a five-fingered hand. In the wings of all these it is the fingers, ormore exactly the hand, which have undergonethe greatest changes in this transformation intothe wing. In the pterodactyle all five fingers are re-tained. The first four, however, are greatlyreduced in size. Three of them are providedwith small claws, and probably served to sus-pend their possessor to some rock or tree duringrest, just as the bat to-day hooks himself up bythe tiny toes of his hind-feet. The fifth, or little,finger was enormously developed, and served asa support to a membrane formed by a drawingout, so to speak, of the skin of the 226 THE STORY OF BIRD-LIFE. Exactly how this was done, and what this wingwas like, can be seen by a reference to ourpicture (fig. 5).. Fig. restoration of an extinct flying lizard or the author. The bats wing differs from the pterodactylesin that all five fingers are well developed. Thethumb in some species is very long and armedwith a powerful claw. The four fingers areexceedingly long and slender, and support athin membrane much after the fashion of theribs of an umbrella. Now compare these two with the wing of thebird. Let us begin with the skeleton. At thefirst glance this will appear to have but one veryshort finger—representing the thumb—and onevery long one, representing the index or firstfinger. If we look at this closely in a veryyoung bird, we shall find that this long fingerreally consists of two fingers closely joined to-gether, representing the second and third digits PEDIGREES—THE FOUNDERS OF THE HOUSE. 227 of our hand. This third digit is in modern birdsvery short, but in archseopteryx it was long andarmed with a strong claw. Now, these two
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