Page:Cyclopaedia, Chambers - Supplement, Volume 1.djvu/811

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The antennae both of the males arid females of fome fpecies have alio their ftalks covered with fingle hairs and at cer- tain diftanccs, or at every articulation thefe have four hairs longer than the reft, and eafdy diftiuguifhable by the naked eye.

The gnats have no fmall or glofly eyes as moft of the other flies have, but in recompence for the want of thefe, they have reticular eyes fo large as to furround, and in a manner cover the whole head. Thofe of many fpecies are extreme- ly beautiful, of a fine changeable green in fome lights, and of a bright red in others.

Many of the fpecies of gnats have before their heads two fmall oblong cylindric bodies, fomething refemblinw the antennae of the fhort bodied flics ; thefe we may not impro- perly call the beards of the gnat, for immediately below them is placed the trunk, and they feem to have fome ana- logy with the beards ot the butterfly clafs, which arc placed in the fame manner. Reaumur* ibid, and p. fcq. For the trunk and wings of the gnat, fee the articles TRUNKand Wings, Gaf-AT-a/tfm, in natural hiftory, a fmall water infect, pro- duced of the egg of a gnat, and which is after its feveral changes transformed into a gnat again.

Thefe worms do not frequent rivers, but ditches, ponds, and other ftanding waters afford them in vaft abundance, from the middle of May, till toward the beginning of winter. This is the reafon why watery and marfhy places are found moft to abound with gnats, and why the wet fummers are found to produce the greateft numbers of them ; becaufe in dry ieafuns, the ponds and ditches, where they are to pafs their worm ftate, are dried up, and the worms killed. Thefe are a creature however, that one need not go far to feek, fence one need only expofe a vefl'el of water in a garden,, or any open place in tbefummcr months, and fooner or later it will not fail to afford plenty of thefe worms. Before thefe worms are arrived at their full growth, though they are then but fmall, they are eafdy found, becaufe they are under a neceffity of coming frequently to the top of the water, by having occafion for frequent refpiration ; and to do this, they are obliged to keep the end of a fmall pipe they are iurndhed with, from the laft ring of their body, above water. The end of this pipe is hollow and in- dented, and forms a fort of funnel on the furface of the water : it is of the length of about three rings of the body, and is fomewhat thicker at its infertion than at its extre- mity.

As there is a vaft number of fpecies of gnats, there is no lefs of the worms from whence they are produced, and to this is in a great meafure owing the variety in the figures given of the worms by the authors who have treated of them ; which may alfo be not a little added to by the par- ticular views in which thofe draughts have been taken. Notwithftanding all the variations of thefe figures, the ge- neral form of the animal is however the fame in all, and the fpecies cannot but be known from any of them. The worm is of the third clafs of thofe which are tranf- formed into two winged flies ; that is, it has no legs, and has a head of a conftant and invariable figure, and has no teeth or moveable jaws formed to play aga'mft one another. Their body is fomewhat long, and the head is detached from the firft ring, to which it is faftened by a fort of neck. This firft ring is the longeft and largeft of all, and feems a fort of corcelet to the worm. The creature lias eight rings befide this, thefe grow fmaller as they approach the hinder extremity.

The tube of refpiration which is fent off from the laft ring, ufually makes an angle with it, and is feldom fcen in a right line with the reft of the body; but befide this there is fent off from the fame ring, another pipe or tube as wide as this, though much fhorter ; this is affixed to the lower part of the laft ring near the belly, and is placed almoft per- pendicularly to the length of the body ; this is the pafl'age for the excrements of the worm, which is often fecn to void green ones through it.

This whole tube is (unrounded with long hairs, and from Its end, from within the hollowed part, there are propagated four very tranfparent, thin, and fcaly oral bodies, which feem intended as fo many oars ; they are placed by pairs, one pair going out from the right hand fide, and the other from the left, and the creature has a power of drawing them toward, or feparating them from one another. Every ring of the body has on each fide about the middle of its length a pencil of fine hairs, but the firft ring which may be compared to the corcelet of flics, is lurnifhed with three of thefe pencils.

While the worm is young, the body is whitifh or greenifh, but when it is at its full growth, and draws near the time of its changes, it becomes greyifh. The great tranfpa- rence of the body of this worm, gives a fine view of what panes within it ; it is at any time eafy to fee into the mo- tion of the inteftines, by which the food is pufhed on to- wards the anus. The two principal trachea? are alfo feen very diftindtly in this creature, they are two white tubes placed in a parallel direction one to another, and run from the firft ring to the tube of refpiration.

G O A

The head is of a browner hue than the reft of the animal,

and is fomewhat flatted ; on each fide one may eafi'ly di- ftinguifh a brown fpot which are the eyes. There are no teeth difcoverable in the mouth, but all about it there are placed a number of fmall beards ; two of thefe are much larger than the reft, and are fomething of the figure of two crefecnts ; thefe are fringed within, and the creature has a power of moving them very fwiftly, and by that means makes a current of water about its mouth, which brings with it the proper food for the animal. The head of this creature is adorned alfo with a fort of antenns ; thefe are bent into a fort of circle, and the con- cave fide of one is turned toward the concave fide of the other. Thefe are antenna? of a very different ftructure from thofe of the winged infects, for they have no articu- lation except that of their bafe. Their concave fide is fmooth and polifhed, and all along the convex fide, there are placed at certain diftances fmall hairs, which look like fo many weak thorns or prickles. And at fome diftancc from the end of each antenna, is a fmall clufter of long and fine hairs.

The great worm, feveral times changes its {kin in the courfe of its life. After three changes of this kind, which ufually happen in the fpace of three weeks, or thereabout, it undergoes a fourth, where the old fkin is as eafily thrown oft as in the reft, but the animal now appears in a new form, that of a nymph : it is now fhorter and rounder than before, and the body is fo bent that the tail is applied to the under part of the head ; this, however, is only its form in a voluntary ftate of reft, for it can yet move, and when it pleafes extends its tail, and fwims about as fwiftly as when in its other ftate.

All the parts of the future gnat may be (een in this nymph ; the fkin of it is extremely thin and tranfparent, yet fuffici- ently tough and firm for the ufe it is intended for. It is uncertain how long exactly the animal lives in this nymph ftate ; but after the time is accomplifhed, its change into the gnat is very quick, and is attended with great danger to the animal, fince multitudes are drown'd, and perifh. in the act of getting out. Reaumur, Hift. Infect. Vol. IV.

GO, in ichthyography, a name given by fome to the common rock fifh, or fea gudgeon, ifrilloughbyh Hift. Pifc. p. 206. See the article Goget.

GOACONEZ, in botany, the name of an American tree which affords a white balfam r but little known in Europe ; it is called by fome authors balfamum album, and by others balfamum purius.

GOAN, the name of a Perfian tree, of the afhes of which they make a fort of antifpodon, or medicinal powder for dif- eafes of the eyes. James, Med. Diet, in voc.

GOARING, on fhip-board. The feamen fay a fail is cut gearing, when it is cut floping by degrees, and is broader at the clew than at the earing, as all top-fails and top-gallant fails are.

GOAT, capra, in zoology, a genus of animals ; the charac- ters of which, according to Mr. Ray, are thefe. That it is covered with hairs, not with wool ; that its horns are lefs crooked than thofe of the fheep, and that it has a beard hanging down from its chin, and is of a ftrong fmell. It is very fingular, that this genus of animals are all able to run and climb about the rugged parts of mountains without falling, though their feet feem by no means contrived by nature for any fuch purpofes. There are eleven known fpe- cies of this animal. 1. The common kind fufficiently known, 2. The capra mambrina or Syrian goat. This is remarkable for the length of its ears, which reach almoft to the ground ; the horns are two or three hand's breadth long, and are very little inflected backwards ; it is of the fhape of the common goat, but larger j its colour is that of the fox ; its horns are black, and its ears very like thofe of the common hunting hound ; it has two appendages hanging from under its throat, and is a creature eafily tamed, and feeds on hay and other vegetables. 3. The capra Afrkana, or African goat, defcribed in the German ephemerides, which is of a dufky grev colour, and has a bundle of erect hairs growing on the middle of its head ; and on each fide, between the eyes and nofe, it has two cavities, which con- tain a thick, fat, yellowifh liquor, which afterwards congeals into a black fubftance, of a mixed fmell, be- tween thofe of mull; and caftor. As foon as the matter con- tained in thefe cavities is taken away there returns more in its place, which is in like manner dried and hardened by the air, Thefe cavities have no communication with the eyes, and therefore the matter defcribed here is nothing of the na- ture of the lacbryma cerz-r, mentioned in the catalogues of the materia medica : this creature is figured without horns, in which it agrees with the mufk animal. The other fpecies are, 4. The ibex, 5. The rupt capra, 6, 7, 8. The three fpecies of gazella. 9. The bufclaphus, and 10, 11. The two trageiaphi, each of which fee under its proper head. ^7/sSyn. Quad. 180. Ephcm. Germ. ann. 14. obf. 57. Goats may be of great advantage to the farmers in fome parts of the kingdom, as they will live in rocky barren countries, where nothing elfe can get a fupport for life. They will

climb