length of tail possessed by nearly all the Cuckoos is given to them as a sort of balance, just as a rope-dancer, with such an instrument in his hands, preserves his footing when otherwise he would assuredly fall. Remote therefore as the Cuckoos unquestionably are from the typical Scansores, we yet find the functions of the tail contributing to that office [i. e. climbing], although in a very different mode to that which it performs among the Woodpeckers, the Parrots, and the Creepers. The structure of the feet, as before observed, is the only circumstance which would lead an ornithologist to place these birds among the Climbers, supposing he were entirely unacquainted with their natural history properly so called, or with their close affinity to the more perfect Scansores. The toes, indeed, are placed in pairs; that is, two directed forward, and two apparently backward; but a closer inspection will shew that the latter are not strictly posterior, and that they differ so very materially from those of the Picidæ (the preeminently typical Family of the Climbers), as clearly to indicate a different use. The organization of the external posterior toe of all the Woodpeckers, Parrots, and Toucans renders it incapable of being brought forward, even in the slightest degree; whereas, in the Cuckoos, this toe can be made to form a right angle with that which is next it in front, from which circumstance it has been termed versatile; this term, however, is not strictly correct, inasmuch as the toe cannot be brought more than half-way forward, although it can be placed entirely backward.... The Cuckoos, in fact, are half perching, half climbing birds, not only in their feet, but, as we have seen,
