This passage was long looked upon as a pleasant story, and nothing more; until M. Geoffroy St. Hilaire, during his long residence in Egypt, ascertained the story of Herodotus to be correct in substance, but inexact in details. It is perfectly true that a little bird does exist, which flies incessantly from place to place, searching everywhere, even in the Crocodile's mouth, for the insects which form the principal part of its nourishment. This bird is seen everywhere on the banks of the Nile, and M. Geoffroy has proved it to be of a species already described by Hasselquist, and very like the small winged Plover. If the Trochilos be in reality the little Plover, the bdella cannot be leeches, (which do not exist in the running waters of the Nile) but the small insects known as _gnats_ in Europe. Myriads of these insects dance upon the Nile: they attack the Crocodile upon the inner surface of his palate, and sting the orifice of the glands, which are numerous in the Crocodile's mouth. Then the little Plover, who follows him everywhere, delivers him from these troublesome enemies; and that without any danger to himself, for the Crocodile is always careful, when he is going to shut his mouth, to make some motion which warns the little bird to fly away. At St. Domingo there is a Crocodile which very nearly resembles that of Egypt. This Crocodile is attacked by gnats, from which he would have no means of delivering himself (his tongue, like that of the Crocodile, being fixed) if a bird of a particular species did not give him the same assistance that the Crocodile of the Nile receives from the little Plover. These facts explain the passage in Herodotus, and demonstrate that the animal, there called bdella, is not a leech, but a flying insect similar to our gnat.