GYRINUS, in natural history, water flea, a genus of insects of the order Cole optera. Antenna: cylindrical ; jaws horny, one-toothed, sharp-pointed ; eyes four, two above and two beneath ; thorax and shells margined, the latter shorter than the body ; legs formed for swimming. The insects of this genus are to be found on the surface of waters, on which they run, and describe circles with a great degree of swiftness; when attempted to be taken they plunge to the bottom, drawing after them a bubble very similar to a globule of quicksilver. Eleven species of the gyrinus have been describ ed, of which one only is found in Europe; and in the United States about six addi tional ones, viz. G. natator, a small insect, not more than a quarter of an inch long, of a blackish colour, but with so bright a surface as to shine like a mirror in the sun. The larva is of a very singular as pect, having a lengthened body, furnish ed with many lateral appendages down the body, exclusively of six legs. Dr. Shaw says, its motions are extremely agile, swimming in a kind of serpentine manner, and preying on the smaller and weaker water-insects, minute worms, &c. It is a highly curious object for the micro scope. When its change arrives, it forms
for itself a small oval cell or case on a leaf of some water plant, and after casting its skin it becomes a chrysalis. These animals, in large numbers, give out a disagreeable smell, and, like other water beetles, they fly only by night Their eggs are white, and are laid on the stems Or It, the eighth letter, and sixth consonant in our alphabet ; though some grammarians will have it to be only an aspiration or breathing.
It is pronounced by a strong expiration of the breath between the lips, closing, as it were, by a gentle motion of the low er jaw to the upper, and the tongue near ly approaching the palate.
There seems to be no doubt, but that our h, which is the same with that of the Romans, derived its figure from that of the Hebrew And, indeed, the Phoeni cians, most ancient Greeks and Romans, used the same figure with our H, which in the series of all these alphabets keeps its primitive place, being the eighth let ter.
H, used as a numeral, denotes 200; and with a dash over it, H, '200,000.