1888. | NEW YORK ACADEMY OF SCIENCES. 97 
sky can be clearly seen between the tips of each of the four or 
five outer primaries, which do not touch each other for several 
inches.’ Furthermore, when the wing is flexed sufficiently 
for the tips of the primaries to overlap, the carpal bones have 
so far changed their position that they no longer “ lock” the 
wing, if indeed that be their function under any circumstances. 
So that, could any advantage be derived from the interlocking 
of the guills, the other alleged conservator of muscular force, 
the interlocking of the bones of the wing, would be sacrificed. 
It has been intimated that the emargination in the primaries 
of hawks and other soaring birds gives evidence of interlocking, 
being apparently a provision for this purpose. ‘That it has sug- 
gested the theory of interlocking is quite evident, but it has no 
further bearing on the subject. ‘That it is not distinctively 
characteristic of soaring birds has been abundantly shown. The 
purpose of this structure evidently varies in different birds. 
In some birds, as the woodcock, various genera of pigeons, 
fly-catchers, and humming-birds, the faleate tips of the outer 
primaries give rise to musical sounds, of somewhat varying 
character in different species, due to the rapidity and angle 
with which they strike the air in rapid flight, the emission of 
the sound being voluntary on the part of the bird, ane often 
forming a part of its amatory demonstrations, as does song or cer- 
tain peculiar notes in many song-birds. In herons, many water- 
birds, hawks, eagles, owls, vultures, etc., it is apparently the 
elimination of a part of the vane which, if present, would prove 
only an impediment and an obstruction in flight. The emar- 
gination extends, it will be observed, from the point where, in 
the fully extended wing, the inner vane fails to fill the entire 
space between two contiguous quills. ‘The vane becomes very 
weak and flexible along its edge, and requires the support of the 
overlying feather to keep it smooth and intact, so that were 
the vane to retain its full width to the tip of the feather, on 
which the air impinges with the greatest force in flight, it would 
have no support from the contiguous feather, and would be too 
weak to resist the air; it would consequently be more or less 
rolled upward at its free edge and prevent the free closing of 
the tips of the feathers ; it would not be firm enough to give 
much sustaining power, would be in the way, and become folded 
and rumpled in the closing of the wing. Therefore just that 
useless and obstructive portion is the part eliminated by the 
1A freshly killed specimen of the red-tailed hawk (Buteo borealis) 
was here shown in illustration of the point that the tips of the primaries 
cannot be in contact in the expanded wing of a soaring bird, and 
that consequently the alleged interlocking is impossible. 
