The Hypanis, a river of Pontus, brings down in its waters, about the time of the summer solstice, small membranous particles, like a grape-stone in appearance; from which there issues an animal[157] with four legs and with wings, similar to the one just mentioned. It does not, however, live more than a single day, from which circumstance it has obtained the name of “hemerobion.”[158] The life of other insects of a similar nature is regulated from its beginning to its end by multiples of seven. Thrice seven days is the duration of the life of the gnat and of the maggot, while those that are viviparous live four times seven days, and their various changes and transformations take place in periods of three or four days. The other insects of this kind that are winged, generally die in the autumn, the gad-fly becoming quite blind[159] even before it dies. Flies which have been drowned in water, if they are covered with ashes,[160] will return to life. CHAP. 44. (37.)—THE NATURE AND CHARACTERISTICS OF ALL ANIMALS CONSIDERED LIMB BY LIMB. THOSE WHICH HAVE TUFTS AND CRESTS. In addition to what is already stated, we will add an account of every part of the body of an animal, taken limb by limb. All those which have blood, have a head as well. A small number of animals, and those only among the birds, have tufts of various kinds upon the head. The phœnix[161] has a long row of feathers on it, from the middle of which arises another row; peacocks have a hairy tuft, resembling a bushy shrub; the stymphalis[162] has a sort of pointed crest, and the pheasant, again, small horns. Added to these, there is the lark, a little bird, which, from the appearance of its tuft, was formerly called “galerita,” but has since received the Gallic name of “alauda,”[163] a name which it has transferred to one of our legions.[164] We have already made mention, also, of one bird[165] to which Nature has given a crest, which it can fold or unfold at pleasure: the birds of the coot kind[166] have also received from her a crest, which takes its rise at the beak, and runs along the middle of the head; while the pie of Mars, and the Balearic crane, are furnished with pointed tufts. But the most remarkable feature of all, is the crest which we see attached to the heads of our domestic fowls, substantial and indented like a saw; we cannot, in fact, strictly call it flesh, nor can we pronounce it to be cartilage or a callosity, but must admit that it is something of a nature peculiar to itself. As to the crests of dragons, there is no one to be found who ever saw one. CHAP. 45.—THE VARIOUS KINDS OF HORNS. ANIMALS IN WHICH THEY ARE MOVEABLE.