So far so good. Next it is to be noted that this syrinx presents a great variety of modifications, or types, differing not only in plan, but also in the number and distribution of the muscles for its manipulation. The most accomplished performers are to be found among that great group of birds known as the Passeres, or perching birds, wherein the number of these muscles is never less than five pairs, and generally rises to seven. This association of musculature with performance is exactly what we should expect. In Nature, however, it is always the unexpected that happens. In the first place, the females are, so far as the dissecting-knife and the microscope can show, as well provided as the males, yet they do not sing. In the second, the Nightingale and the Crow are equally endowed, so far as we can discover, yet it is unnecessary to state that the talents which the Crow possesses are never used! More disconcerting still is the reflection that the Parrot, which is far less generously endowed by Nature in so far as singing muscles are concerned, is a much more skilful performer, inasmuch as it will reproduce with equal fidelity the human voice and the song of the Canary! The latter feat, at any rate, has been accomplished with amazing accuracy both by the little Budgerigar (_Melopsittacus undulatus_) and the Quaker Parrot (_Myopsittacus monachus_). In their wild state the Parrot family are notorious for their discordant cries. It is therefore the more remarkable that such feats should be capable of attainment. But wherefore the elaborate syrinx of the Nightingale, if the simple type seen in the Parrot is capable of the same result, and why the elaborate syrinx in the case of the Crow, which never attains to a greater perfection of vocal effort than the wild Parrot? One speaks of the syrinx of the Parrot as of a simpler type because of its feebler musculature and the lesser complexity of its framework, but it is nevertheless a more efficient instrument, since it is capable of reproducing both the human voice and songs such as that of the Canary. This fact becomes still more remarkable when we reflect that the natural voice of the Parrot, as we have just remarked, attains to no more than a harsh screech. How is it that, capable of so much, it has achieved so little? The same question may be asked in the case of the Raven. This bird has a syrinx indistinguishable from that of the Nightingale, save in point of size; yet the Raven’s voice is never musical, nor can it be trained to such an achievement. Like the Parrot, however, it can be taught to speak, though its vocabulary is never so extensive. One would have imagined that when the syrinx of, say, the Raven, or any of the Crow tribe, was compared with that of the Nightingale or the Skylark, some structural differences, commensurate with the difference in performance, would be discovered; but such is not the case.