In form, too, they vary exceedingly. Some are very slender, and apparently feebly constituted; others are comparatively quite robust. There are species which have bills excessively long, the _Sword-bearer_ (_Trochilus ensiferus_), which is about the size of the House Wren, has a bill longer than its body. So entirely disproportionate does the bill of this species appear to be, that few persons, on seeing specimens for the first time, can avoid a suspicion that it has been artificially lengthened; and we have more than once heard it suggested on such an occasion that this remarkable appendage could readily have been drawn out by processes used by comb-makers. This exceedingly long bill is, however, no inconvenience whatever to the gay little individual who is responsible for it, luckily for him;—in fact, it assists him admirably in procuring an entirely honest subsistence amongst the large trumpet-flowers, and others with long tubular corollas, abundant in tropical countries. No other known species has this organ of a length so disproportionate, though there are several in which it is unusually long for birds of such size. The bill is, however, scarcely of the same form and shape in any two species. In some, it is perfectly straight and very short; in others, as we have already observed, it is very long. Numerous others have the bill curved downwards, or scythe-shaped, and a few species have it turned upwards, presenting a very singular appearance. Other curious appendages are to be met with in species of this family. One group has exceedingly long tails, three or four times the length of the body. Several Humming Birds have the outer feathers of the tail long, and though narrow for the greater part of their length, suddenly expanded at the end like a paddle or a spoon. These seem to form a group or sub-genus of their own, and are also remarkable for having the upper part of the leg (the _tibia_, and sometimes part of the _tarsus_) covered with a thick mass of white downy feathers, presenting one of the many instances of phenomena to which it appears almost impossible in the present state of our knowledge, to assign a use in the economy of the species. The wings in all Humming Birds are large, when compared with those of many other birds, and are formed for long-continued and rapid flight.