Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/277

 POL

Pol

C/«y?.r-PoLYPE, the name of a fpecies of fmall infect of the polype kind, called by the French natural! its polype a bouquet. There is found on feveral of the water-plants, and on other fuhftances, as flicks, boards, and the like, accidentally fallen into the water, a whitifh fubftance that at firft fight appears to be only a fort of mouldynefs ; hut if the bodies on which this is found, be put into a veflel of clear water, and the matter examined with a magnifying glafs, it is foon feen that this whitifb fubftance is really a vaft number of ("mail animals, which are almoft continually in motion. When this is brought before the microfcope, the form and ftrudture of the creatures is very evidently diftinguifhed, and they are found to be mi- nute roundifh creatures, feverally affixed to the end of a fort of item or tail J and many of the items are fo interwoven and united together, that they form duflers, which have occa- fioned the name of the dufler- fo'ype to be given to the animal, tho' in itfelf it is really and properly fingle from the begin- ning- There are feveral fpecies of polype of this minute kind, that dufler themfelves in this manner together ; and according to thefe and other circumftances, the duflers are found larger or fmaller, and more or lefs complex. Phil. Tranf. N" 474.

P l l r -

The fmaller dujlers fhould always be chofen for obfervation, as in the larger the bodies of the feveral animals that compofe them are apt to hide and obfeure one another; but the tnoft beautiful and accurate of all obfervations is to be formed when they are fingle, as they are fometimes found ; and this is the only opportunity of feeing diftinctly in what manner the duflers are formed.

One of thefe fingle animals is not in length above the 240th part of an inch, and is of a ihape nearly refembling that of a bell : the anterior part of this generally appears open when it prefent's itfelf properly ; and the pofterior part is fixed to the item or pedicle, by the other extremity of which the crea- ture fattens itfelf to any folic! body that it meets with. The body is of a brownifii colour, except at the fmaller end, which as well as the tail is whitifh and tranfparent; and when the anterior part is open, there may always be perceived about its edges, a very lively motion ; and when the creature prefents itfelf in a better manner, there may be feen on either fide of the edges of the anterior part, fomewhat refembling the wheels of a mill, continually moving with great velocity. Thefe creatures are able to contract their bodies, and often do it very iuMenly, efpecially if any thing difturb the fub- ftance on which they are fixed : when they are thus contract- ed, the edges of their anterior parts are drawn juft into their bodies ; and when the fright is over, it is a very agreeable fight to behold thefe edges turning out again, and putting themfelves in motion as before. If the edges of the anterior parts of the bodies of thefe animals be ftrictly obferved while in motion, the water about them will be found to be full of extremely minute round bodies which are brought together by means of that motion, and ferve the creature for its food : thefe may be often feen going down into the cavities of the body of the polype, and that very fuddenly, as if forcibly driven down ; and when fwallowed too voracioufly, are often thrown up again. Thefe obfervations are heft made when a finall dufler of the polypes are examined together. If thefe polypes are kept (ome time in the rain-water, they by degrees lofe their brown colour, and become white and tran- fparent throughout, except that a few fpots of a dufky co- lourremain in their bodies ; but if after this they are removed into other water of the fame kind with the fir/I, but newly taken out of the ditch, they in a little time recover their brown colour. When they become white, they plainly ap- pear to be in a fickly condition, and ceafe to multiply ; but when they have frefii water and recover their colour, they im- mediately begin to multiply again.

Thefe creatures are not abfolutelv and immovcably fixed to the bodies on wWlch they are placed, but they can at pleafure quit them and fwim about : in this fwimming ftate they are always found fingle and not in duflers ; and they do not then appear in the fame form as when they are fixed and open at their anterior ends. When they have fwam about as long as they pleafe, they either return to their dufters from which they feparated themfelves, or affix each fingly to any thing they meet with: and this is a circumftance that merits to be carefully watched, becaufe it is by means of this that we fee in what manner the creature multiplies itfelf, and the duflers are formed.

As foon as a fingle animal of this kind is fixed to a flick, a ftone, or any other fubftance, it begins to lengthen its ftem or tail, which tho' very fiiort while fwimming, and when firft fixed, very foon becomes of its priftine length while in the dufler; and after this the creature begins immediately to mul- tiply by the moft amazing means in the world ; that is, by fpliting itfelf to pieces lengthways. The firft motion toward? this operation is the drawing in the lips or edges ; this is foon done, and the body then lofes its bell-like ihape, and becomes round; the motion which was before perceived at the ed^es ccafes, and there is only a flight tremulation to be feen with- in the body; after this the- amerior part of the body becomes fiat and broad, and the whole body martens in proportion; and foon after this the whole body gradually fplits itfelf re-

gularly into two, from the center of the anterior part to the center of the hinder end, where it joins the tail or pedicle, and there foon appear two round and perfect bodies joined to that pedicle which before 'upported only one. The anterior parts of the two bodies foon begin to open, and gradually fhew their edges, which perform the fame motion the finglepne did before. The motion is at firft very flow, but it grows quicker by degrees as they open ; and when they are perfectly ex- panded, it is as quick as it was in the original fingle body : it is at this time that the two bodies may be cfteemed quite perfect. They are at firft indeed lefs than the original polype, from which they were formed, but they grow to the fame fize in a very little time : the whole operation of dividing it- felf, takes up the creature about an hour ; but to form a true idea of the manner in which it is performed, there muft be many obfervations made, and the creatures muft be examined in ail views and lights while about it.

The lips of thefe polypes, when clofely examined, appear to be compofed of four or five tranfparent bands, all which have an undulatory motion. And when the newly divided polype is but flow in its motions, it is eafy to difcover that what af- terwards appear to be like the wheels of a mill, are, in reali- ty, only iour or five oblong bodies, refembling a fort of fin- gers which alternately bend down, and extend themfelves every inftant. Thefe are fattened to the bands of the lips on each fide of the mouth; and when they are put into fwift motion in the time of the full growth and vigour of the animal, they are not to be diftinguifhed, as to form, nor can their motion be otherwife difcovered than by its fwiftnefs, which makes it refemble the quick turning of a wheel.

When the feparation of the body of a fingle polype of this kind is compleat, one fees two regular and perfect bodies ad- hering fide by fide to the fame pedicle, but foon after each of the new formed bodies begins to mew a pedicle of its own ; thefe grow in a day's time to a moderate length, and unite at their bottoms to the end of what was the original fingle pedicle of the body while but one; they grow to this in the manner of the branches growing to the trunk of a tree. Twenty-four hours after the feparation of the original body into two, thefe two begin to feparate themfelves in the fame manner, each into two again ; and thefe after a like time again feparate : each of thefe feparated animals has its own tail formed in a like period of time with the firft; and the con- fequence is, that the firft feparation producing two, the fecond gives four, the third eight, and fo the fixth fixty-four, the feventh 1 28, and fo on; by which means a fingle animal, in a very few days, forms out of itfelf an immenie dufler ; each animal of which is perfect in itfelf, and independent of all the reft, and can, when it pleafes, fwim away and form a new dufler. They will multiply as fail in gl. fs jars, as in their native free ftate in the waters, andcluflers. of them, be- , gun near one another, will often join in fuch a manner as to form one complex dufler of an inch diameter : from thefe fe- veral duflers there detach themfelves fingle pol\\es from time to time, which go ofF and fattening themfelves to other bodies, become the authors of new progenies. Phil. Tranf. N 3 474.

P-/75-

The original branch or ftcm of the firft polype, remains always in the center of the dufler ; but it is of no ufe, never after- wards having any body fixed to it.

There are, befide this fpecies here defcribed, four other known kinds of polypes, which divide themfelves in the fame manner by fpliting into two lengthwife : thofe which come nearcft to the firft are flenderer, and their items are more tranfparent. They are of a bluifh colour, when many of them are feen together, and their items or tails very aptly refemble fpun glafs. When this fpecies is perfectly formed, the motion of its lips is lefs diftinct than in the other ; but it may be difcovered in the fame manner while they are newly feparated and are but growing toward perfection, when it gradually becomes lefs and lefs diftinct.

Another fpecies of thefe polypes is fmaller than the laft, but more open at the mouth and deeper hollowed ; and thefe are particularly diftinguifhed from all the others, by having amo- tion in their items and branches, which all the others want. The items draw themfelves up, and fhorten all at once into the appearance of a fpiral fcrew, and in a moment can dart themfelves ftrait out to their full length again. All thefe mul- tiply very fpeedily, but they have all enemies that deftroy them in a very terrible manner, whole duflers making but fingle mouthfuls. The funnel-polypes are nearly allied to thefe crea- tures. Phil. Tranf. N« 474. p. 180. Famid-PoLYPE, a name given by natural ifts to a fmall water- infect, in fume refpects approaching to the nature of the cluf- tzr-pdype. See Clufler Polype, fupra.

The funnel polype nearly refembles a funnel, from which it has its name. It is long and hollow, and very wide at the an- terior end. Thefe little animals are of three fpecies, a green, a blue, and a white one : they are all too minute for the ob- fervation of the naked eye, and muft be viewed with great caution, and in feveral different directions and attitudes, be- fore their true form can be difcovered ; and their anterior end, particularly, when carefully obferved, is of a much more 2 compound