690 BIRDS. 
Pedigree. — Birds have many structural affinities with 
Reptiles ; some of the ancient Dinosaurs present approxi- 
mations to Birds; the extinct flying Pterodactyls show that 
it was possible for flight to be developed among Reptiles ; 
the oldest bird — Archaeopteryx —is in many ways a 
connecting link between the two classes; and the develop- 
ment of some Birds reveals many remarkable resemblances 
with that of Reptiles,—therefore, with the strength of the 
general argument for evolution to corroborate us, we 
conclude that Birds evolved from a Reptile stock. 
It is likely, then, that Birds arose from an ancient Saurian 
stock, but by what steps and under what impulses we do 
not know. To some it seems enough to say that the 
evolution was accomplished gradually in the course of 
natural selection by the fostering of fit variations and the 
elimination of the disadvantageous ; to others it seems that 
the incipient birds were “fevered representatives of reptiles, 
progressing in the direction of greater and greater con- 
stitutional activity”; but both these suggestions leave 
much in the dark, leave us still to “wonder how the 
slow, cold-blooded, scaly beast ever became transformed 
into the quick, hot-blooded, feathered bird, the joy of 
creation.” 
