A BIRD’S FOREFATHERS. 5 
special glands (7amme) to nourish their young as the 
mammals. 
While they differ from each other in the bird hav- 
ing hot blood and feathers (instead of cold blood and 
scales), great naturalists are inclined to make one class 
cf the two groups. The oldest bird which we know 
of yet is the fossil Archwopteryx, and had not the print 
of the feathers on its wings, tail, and legs been left in 
the rocks along with its bones, it is probable that it 
would have been classed simply as a flying lizard. 
Thinking back over what has been noted, we may 
say of the bird that it is— 
A back-boned, four-limbed, lung-breathing, egg- 
laying, hot-blooded, feather-covered, upright-walking 
creature, having its fore legs adapted to flight; for, 
however flightless a bird may be now, there is sufhi- 
cient evidence that it has come out of an ancestry 
whose wings were once really complete and useful. 
Whether all birds have had the same forefather 
is a much discussed question out of place in this con- 
nection, but it is further slightly referred to in Chap- 
ter ILI. 
