61 
buoyancy tothe body. It doesnot like the albatross 
depend on its own unassisted exertions for food. “Te 
lives by rapine, and the prey which the gull and the 
sula seize, are yielded to the assaults of the frigate- 
bird to supply its wants and satiate its appetite. 
With all the means resulting from the best adapted 
form for flight found in the swallow tribe, on the 
gigantic scale of a bird of the largest dimensions, 
muscular power, lengthened wing, and a long and 
forked tail, it exhibits similar feebleness of feet. 
The same untiring flight and velocity of movement 
stamp both as dependent on the capture of prey, 
while that prey is moving through the air. Thus 
the frigate-bird darts upon the flying-fish, when 
they betake themselves to the air to escape their 
pursuers in the water ; seizes the falling prey dis- 
gorged by the booby and the gull, when those birds 
are attacked and compelled to surrender it. 
Let us go more minutely into the structure of the 
frigate-bird, to illustrate the versatile power of 
buoyancy in the pelicanidz. 
The capacious sack constituting the peculiar 
_ throat-pouch of the tachypetes does not form one 
uninterrupted chamber, but is intersected by some 
three septa or divisions, and seems a prodigious ex- 
tension of the interclavicular or furcular air-cell. 
Air blown into the trachea by the blow-pipe in a 
bird dissected by the late Dr. Chamberlaine, in my 
presence, did not affect this pouch ; the communica- 
tion appeared to be in some way from the mouth by 
the cervical air-cells. The dissection of this part 
of the bird had proceeded too far, for any decision 
! E 
