two or three bristles, serve the same purpose. Further, in 
the case of the bee it will be found that the fore-wing, when at 
rest, is folded longitudinally back upon itself. 
Finally, turn to the flies. Herein it will be seen that 
there is but a single pair of wings, the hind pair having become 
reduced to mere stumps, known as “‘ balancers.”’ 
Much, very much more, might have been said of these 
wings: but our conversation is of birds. We cannot, how- 
ever, properly appreciate either the essential characters of 
their wings, or their flight, without some such standards of 
comparison as is afforded by the wings of other creatures. 
147 
