﻿EXTERNAL ANATOMY. WING FEATHERS. 85 



there exists in the middle a distinct notch, or sinuosity, 

 to break the passage of the air — a structure which is 

 only carried to its maximum in the bee-eaters. The 

 tertials are very little longer than the secondaries, and 

 hardly exceed the shortest of the primaries. It is thus 

 obvious that nearly the whole power of the wing is 

 thrown into the ten principal quills, which are those 

 principally employed in all birds to cut the air, but 

 which, in the present family, are most particularly 

 adapted for that purpose. There is nothing materially 

 different from this structure in the wings of the sea- 

 swallows, as they are aptly termed, or the terns, except 

 that the lesser quills are even shorter, and instead of being 

 notched, are pointed in the middle, while the tertials 

 are longer, and gradually become attenuated at the end, 

 like the primaries. Such is the formation of an acu- 

 minated wing, when seen in its full development. To 

 note all the modifications that this form undergoes in 

 its declension would be tedious, if not impossible. In 

 the bee-eaters (Merops) the shorter primaries, the 

 whole of the secondaries, and a part of the tertials, are 

 deeply notched (fig. 42.) ; but the greater elongation 



of the two latter ranges of quills clearly shows a dimi- 

 nished strength in the primaries, and indicates that 

 these feathers are not so much called into action as they 

 are in the swallows. Accordingly we observed, while 

 in the south of Europe, that the flight of the Merops 

 apiaster, although swift, was effected by very little 

 motion of the wings, and that a swallow would beat the 

 air three times when they would only do so once. 

 Their flight, indeed, is more like that which is called 

 tailing, and they are enabled to do this by the greater 

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