170 THE STORY OF THE BIRDS. 
the rails on the aquatic. Some of these latter have 
such poor wings that it has been believed by some 
unthinking folks that they turn to frogs in the fall 
instead of migrating—a theory on a par with that 
which formerly held that swallows hibernate in the 
mud of shallow ponds. 
A redevelopment of the wing as some of the birds 
took more to flight again has probably given us, out 
of the region between these two short-winged groups, 
such long-winged birds as some of the plovers, all 
the gulls, petrels, pelicans, and some others. The fast 
hawks, the swifts, etc., have also shorter winged kins- 
folk, out from which they may have come. 
Others, as the divers, have remained short-winged 
because of the small amount of flight resorted to, since 
they depend upon swimming and diving so largely as 
a means of escape and foraging. 
It is not improbable that the penguins, with finlike 
wings and reptilelike drumstick (with both bones pres- 
ent), and their many other very primitive peculiarities, 
may have been aquatic ever since their early develop- 
ment, and that their ancestors went directly from flight 
to water, never having, as noted, passed through a 
ground-haunting ancestry. Some of them are said 
to make no use at all of their feet in swimming ex- 
cept as rudders, and they strike first with one wing 
and then with the other in diving—a very unflight- 
like motion, as if they began swimming before they 
ceased crawling. Still, a biological study of the strue- 
ture of their wings hints of a time of flight in their 
past, but that their wings were never brought to a 
