A BIRD’S FORE LEG. 15 
sparingly of bipedal motion in birds. While the 
Archeopteryx could evidently stand upright, and had 
almost a perfect perching foot with a lmb-clasping, 
opposable toe, there is much about the bones of its 
feet and legs that implies that 2¢ did not come from 
an upright ancestry very far back. But some of 
the ostrich forms, living and fossil, which have their 
skeletons adapted to running, show such close re- 
semblance to some fossil reptiles which are known to 
have walked bipedally long before flight that they 
tend to give us the impression that they are lineal de- 
scendants of these terrestrial reptiles. The absence 
of any muscle-holding ridge on their breast bones and 
the smallness of these breast muscles may imply that 
they had never attained to fluttering up flight, and 
that their wings had degenerated from an imperfect 
condition as their bipedal motion had further developed. 
This is not likely the case, however. In such other birds, 
akin to the strain of the Archwopteryx, perfect bi- 
pedal motion seems to have been the result rather of 
the fore leg’s complete development into a model pin- 
ion, while it was useful at first to walk or craw] with. 
It may be, therefore, as held by many thinkers, 
that by more than one route the birds have come out 
of the region of the reptiles; but others feel that 
every wing to-day, from penguin to thrush, is the de- 
scendant of a single type in the beginning, moditied 
by various developments and degenerations. 
Certain it is that if we knew the history of a bird’s 
fore leg, we should know a great deal more about its 
forefathers. 
