URT
USN
contained '» tlis reft of the purfe, but never fills it, unlefs when the mouth of the purfe or covering is clofe drawn toge- ther. The whole covering is a collection of mufcles which are all tubular. The bafe of the fifli never appears to us, be- caufe always fixed down to the rock ; but when the creature is railed from that pofition, and the bafe examined, it appears compofed of a vaft number of tubes placed one behind ano- ther, and running from the center to the circumference. Thefe tubes are often filled with an aqueous liquor, which may be forced out on preffing them. Befides thefe tubes, there are alfo to be feen many circular ones, which fur- round one another, and have for their common center that_ of the bafe. The conic part of the covering is in the fame manner compofed of a number of circular tubes, which are placed very clofe to one another, and all run parallel with the round verge of the bale, and terminate at the upper circle or rim of the cone. Under thefe there is another feries of ftrait tubes, which all run from the bafe to the top of the cone. It is remarkable that the circular and ftrait mufcles are never feen together in the fame place; whether it be that the extending of the one fet makes the others flaccid, or only that the lefs extended ones are hid by thofe which are mote fo. Sometimes there are only the circular ones vidble, fometimes only the (trait ones, and often only a tew of the circular ones appear, refembling fo many bands, between which it is eafy to fee the parts of the ftrait ones which lie under them. The creature feems capable of making all thefe changes at pleafure, filling fuch as it will with an aqueous liquur, which is the caufe of their becoming more vilible, and which is let out, if they are pricked with the point of a pin. The inflation of different parts, of thefe ranges of ftrait and circular tubes, is what makes all the differences in the fhapc of the fifh, and ferves alfo to the purpofe of its pro- greflive motion ; and it feems probable that the aqueous liquor which ferves to diftend them, is, at the pleafure of the crea- ture, conveyed to them from the horns, and from them back to the horns again. The progreiTive motion feems thus per- formed : When the creature has determined which way it will inarch, it diftends all thofe longitudinal tubes which are on that fide of its body which is placed toward the point it would move to ; this, from its round fhape at the bafe, gives it an oblong one; that is, it throws the fore-part fomewhat forward upon the rock ; and, at the fame time, if the lon- gitudinal tubes on the oppofite fide of the body be all left empty, and the circular ones diftended, thefe naturally draw the whole body toward the fore- part, and thus a fmall advance is made and preferved, and this, often repeated, is the flow progrcftion of this animal. All this is, however, performed lb very flowly, that though there is a continual change going on in the creature, both as to fijape and place, yet if the eye is kept continually on the object, . neither is perceived ; but, if taken off for fome time, and the place and figure both kept in mind, both will be found to be altered on viewing again.
There is a fpecies of this fifh alfo which moves by means of its horns; this is. known from the reft by the. length of the horns, and their being covered with a glutinous moifture. This fpecies lives in the cavities and holes of rocks; and when it has a mind to move, it turns itfelf bottom upwards, and crawls flowly on by means of its horns, which then touch the rock.
The food of the XJrt'tca-mar'ina is not lefs wonderful than its ftruilure and motions. It fhould fecm very ft range that an animal, foft like this creature, with no feet, no inftrumcnt of that kind to help itfelf with, fhould he able to feed on the flefh of mufcles, fea-fnails, and otiicr fhcll-fifh ; yet thefe are its conftant food. They find means to take in the fhcll-fifh. whole into the body, and then clofe the aperture faff upon it, fo that it is not to be feen. that they have any fuch thing within them ; they keep them here as long as they pleafe, and after- wards throw out the empty (hells by the fame aperture, which they can, as before obferved, widen and contract at pleafure. By what means the Urtica is able to get out the body of thefe fifh, is not known, as it all pafles in the body; but it very often fails, and the creature is obliged to throw out the fhcll fifh alive again ; and fometimes, when it has greedily gorged too large a morfel, and it is got into a wrong pofition to be thrown out the fame way, it is obliged to let it through the bafe, where there is no natural aperture, and where its paflage muft be attended with a terrible wound. The manner in which the larger (hells are thrown out by the mouth, is by opening it extremely wide, and turning it back, fo that the infide appears outward for a little way down ; and this motion is alfo ufed on another very neceffary occafion, the excluding the young ones, for thefe animals are viviparous. Mem. Acad. Par. 171c.
It has been found that this creature has the remarkable pro- perty of the polype, in re- producing fuch parts as it had loft. Mr. Reaumur tried many experiments on the various fpecies of this, and of the ftar-fifh kind, and found that whatever parts were cut off, the wound foon healed ; and Mr. de Villars had opportunities of watching the whole progrefs of the growth of the animals afterwards, and found that they not only feemed
alive and well after cutting, their wounds foon cicatrifing, but that they,- in a very little time, regained what had been cut off, and became as perfect as before.
URUS, in natural hiltory, the name of a fpecies of wild bull, of a very remarkable fize and ftrcngth. Csefar, in his com- mentaries, has defcribed them as little inferior to elephants in fize, and refembling the bull in fhape, figure, and colour. He adds, that they were very fwift and fierce, and had horns very much larger, and very different from thofe of the com- mon bull. And Mentzclius tells us, that it is a vaft and ter- rible fpecies of wild bull, common in Livonia, C5r. and that when killed, its brain is found fecnted like mufk. Mr. Ray wifhes very much, that fome one, who has an opportunity of feeing this creature, would give a more accurate and perfect account than thofe we already have of it. Ray's Syn. Quad p. 70.
USNKA, (Cycl.) in botany, the name of a genus of modes, the characters of which are thefe: They are wholly deftitute of leaves, and are compofed only of long {lender filaments or (talks, which are ufually folid, rigid, and of a cylindric figuYe. The extremities, or other parts of thefe, are at times furnifhed with a fort of orbicular bodies, dry and deftitute of ui'e^ but fceming to fupply the place of flowers. Thefe are hollow, in form of cups, but have no rim. The whole plants are fixed in the manner of mifletoe to the barks of trees. Michel! has given accounts of flowers and feeds in thefe plants ; but Dille- nius fufptfls the accuracy of the obfervation, and adds,- that if there are fuch, they are too minute to be of any fervfee m the. general diftindfions of the plants. Dillen, Hift. Mufc. p. 68. Of this genus of plants there are nineteen known fpecies. 1. The ftringy-tree mofs, or common XJjnca of the (hops. This confifts of long and variuufly implicated threads, which are branched out into feveral divifions ; this grows on old oaks, and other trees, in thick woods. 2. The wide-forked tree XJfnea, with finer points, defcribed by Micheli, and in its fe- veral varieties, by him called of three fpecies. It is compofed of thicker branches than the former, and they are only dicho- tomoufly divided, having no fmall branches but at the points or ends. 3. The wide forked XJfnea, with thicker points ; this and the two former are of a grey colour, and this com- pofed of rough rufhy branches. It grows on old fir-trees. 4. The capillaceous knotty tree XJfnea, called the long beaded XJfnea, or necklace mofs. This is of a bluifh-grey colour, and hangs down from the branches of old trees. 5. The flat Al- pine XJfnea. This is fofter than the others, and has long and flatted branches, and commonly is found on the larch-tree. 6. The beard Ufnca. This is compofed of thin and fibrous branches, and is ufually more or lefs knotty. It is of a pale grey colour, and grows on old beech, and other trees. 7. The black mane XJfnea, This grows in great plenty in the Hartz Foreft, and in fome parts of England. It is rigid, and of a rufty black. 8. The black, hard, woolly XJfnea. Tins grows on rocks and ftones, and refembles flocks of black wool, but is more rigid. 9. The black tufted XJfnea. This alfo grows on ftones ; it is fmall and (lender, but ufually ftands in thick tufts. 10. The hard and rigid tree XJfnea, with branches expanded every way. This is of a greenifli grey, and grows on oaks, and fometimes on rotten pofts and old boards. 11. The horfehair TJfnea. This is black, and compofed of (lender filaments, fcarcc at all branched, refem- bling horfe-hairs. It is common on" the barks of trees in Pata- gonia. 12. The common (m:JW XJjnca, without r undies or cups. This is a very common" mofs on old trees and boards ; it is very much branched, and does not hang in long firings, like the others, but is of a fomewhat fhrubby appearance. 13. The common (mailer XJfnea with rundles. This is not lefs common than the former, and much refembles it ; but the lateral branches are more rigid. 14. The true XJfnea of the Arabian phyficians. This is of a whitifh colour and fmooth furface, and is divided in the manner of a (tag's horns, and of a very agreeable fmell. The branches are partly cylindric, but a little comprelled, and are ufually crooked, and divided into many filaments. It is not a native of England, but is very common in the Eaft Indies, and in many other parts of the world. Bellonius fays, that it is commonly fold in Con- ftantinople. 15. The orange-coloured forked Ufnca. This is of a deep yellow, and confifts of flatted branches, dichoto- moufly divided, and terminating in fine (lender filaments. It is often found of a foot in length, and is common in the Ca- naries. 1..6. The brafs wire XJfnea. This is of a fine*gold yellow ; it's branches are cylindric and rigid, and it grows up in the form of a fmall fbrub. 17. The (mailer yellowifh tree XJfnea 1 with coronated rundles. This is fmaller, and of a paler yellow than the other, and its branches are thicker. 18. The fmall hairy black XJfnea. This grows on ftones and rocks, and is very fhort and rigid. 19. The (mailed of all the Ujneas. This is of a black colour, and grows on the barks of old trees, but is fo fmall as to be fcarce vifible. Dilten. Hift. Mufc. p. 70.
USNEN, in botany, a name given by Avifenna and Serapion to the plant Kali, of which the alkali fait called pot-ajbes, and ufed in the compounding our (bap, is made. There are alfo fe- veral other things called by this name, and, In general, all that
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