VERMES. 



body alternately more and leh convex. When the tide ebbs, 

 many of them are left on the fhore motionlefs. Although 

 thefe creatures are very numerous, and in fome iiiftances of 

 great bulic, their ftrufture «nd economy are hitherto but 

 little known. Meflrs. Peron and Le Sueur devoted their 

 attention to them very particularly in their voyage to the 

 Soutliern iflands ; have delineated fome Ipecies in their 

 " Voyage aux Terres Auftrales ;" and have announced a com- 

 prehenfive work on the whole tribe, in which their natural 

 hiftory and ftrufture are to be amply invelligated. Perhaps 

 this has even now appeared ; but we have not feen it. In 

 the notice of this publication, given in the Annales du Mu- 

 feum d'Hiiloire Naturelle, torn. xiv. p. 218. et feq. they ob- 

 ferve, " that the fubftance of the medufas is refolved entirely, 

 by a kind of inftantaneous fuilon, into a fluid analogous to 

 fea-water ; yet the moft important funftions of life are ex- 

 ercifed in thefe bodies, which feem to be merely coagulated 

 water. Their numbers are prodigious, yet we have no cer- 

 tain knowledge of their mode of generation : they are in 

 fome cafes feveral feet in diameter, and weigh tifty or fixty 

 pounds, yet their fyftem of nutrition efcapes us : they 

 execute the moft rapid and continued movements, yet we 

 can difcover no fibrous or mufciilar ftrufture : their fecre- 

 tions are exceedingly abundant, yet we fee nothing of the 

 mechanifm by which they are executed : they have refpira- 

 lion of a very aftive kind, but its feat is a myftery : they 

 appear very feeble, yet fifties of fome inches in length are 

 their conftant prey : their ftomach feems incapable of any 

 aftion on the latter animals, but they are digefted imme- 

 diately. Several of them contain air in their interior ; we 

 do not know how they can derive it either from the atmo- 

 fphere or water, or develope it in their inteftines. Several 

 are phofphoric : they ftiine in the darknefs of the night like 

 fo many globes of fire ; yet the nature, the principle, and 

 the agents of this ftriking property are fo many problems. 

 Some fting and benumb the hand which touches them : the 

 caufe of this phenomenon is equally unknown." The latter 

 property, being one of the moft obvious, has influenced 

 the name of thefe beings : they are called in all languages, 

 fea-nettles. 



In the fame volume of the Annales du Mufeum, the au- 

 thors quoted above have given a view of the generic and fpe- 

 cific charafters of the medufae, as they will be defcribed in 

 their great work. See p. 325, et feq. 



The echino-dermata of Cuvier are the moft comphcated 

 in their ftrufture among the zoophytes : they have a coria- 

 ceous or calcareous covering, a diftiiift internal refpiratory 

 organ, and often numerous retraftile feet. In many the 

 fliin is of a more or lefs cruftaceous nature ; or it may even 

 be a true fliell. The feet, parting through apertures of this 

 covering, admit of being extended or withdrawn : they are 

 often arranged with much regularity. There is a mouth, 

 provided generally with five teeth arranged in a circle, and 

 leading into an alimentary cavity in the interior of the body : 

 there are alfo ovaries ; and a very extenfive ramified organ, 

 which feems to eftablifti a perpetual circulation of water 

 through the bodies of thefe animals, and confequently a 

 kind of refpiration. Nothing is found Hke heart or brain. 

 The holothuria (fea-cucumber), with its cyhndrical body 

 and thick leathery Ikin ; the atterias, with its conical radiated 

 procefles and pliable calcareous integument ; and the echinus 

 (fea-hedgehog), with a complete calrareous ftiell, belong to 

 this divifion. 



The medufx, ftar-fifti, echini, &c. are formed by La- 

 marck into a diftinft clafs, which he calls Radiana, or 

 radiated animals, becaufe their bodies are diftinguifhed, in 



the arrangement both of their internal and external parts, 

 by being formed into radii furrounding a centre ; a form- 

 ation of which the firft (ketch is feen in the polypes. 



Their mode of generation is not exaftly known, but they 

 pofTefs confiderable powers of reproduftion : they contain 

 organs that feem hke ovaries. The mouth is placed down- 

 wards, or on the inferior furface of the body : they have no 

 head, eyes, nor articulated limbs, probably no nerves ; and 

 no circulating fyftem. 



This clafs comprehends two orders : 



I. Radiaria mollufca (foft radiant animals). Gelatinous 

 body, foft tranfparent ikm, without any articulated fpines ; 

 no anus. Genera : Stephanomia. Lucernaria. Phyffopho- 

 rus. Phyfalia. Velella. Porpita. Pyrofoma. Beroe. 

 Equorea. Rhizoftoma. Medufa. 



II. Radiaria echino-dermata. Opaque cruftaceous or co- 

 riaceous flcin, furniftied with retraftile tubercles, or fpines 

 articulated upon tubercles, and perforated by rows of holes. 



1. Stellerida. Skin not irritable, but moveable; no anus. 

 Genera : Ophiurus. Afterias. 



2. Eclunida. Skin not irritable, nor moveable; an anus. 

 Genera : Clypeaftrus. Caffidites. Spatanguis. Anan- 

 chites. Galerites. Nucleolites. Echinus. 



3. Fiftuljda. Body elongated ; ikin irritable and move- 

 able ; an anus. Genera : Holothuria. Sipunculus. 



The vermes of Cuvier approach very much to the larvae 

 of infefts. Perfeft infefts are diftinguiftied, among all the 

 white-blooded claftes, by the perfeftion of their organs of 

 motion, their members having diftinft articulations, and the 

 component parts being fohd. The larvae in fome cafes en- 

 joy the fame advantage : thofe of the orthoptera and heraip- 

 tera have as perfeft legs as the perfeft infefts : iii the larvae 

 of the lepidoptera and coleoptera, the members are generally 

 very ftiort, and not capable of prompt motion. The limbs 

 difappear entirely in the larvae of the diptera, and many of 

 the hymcnoptera, their place being fupplied by hairs, 

 briftles, or merely by the rings and tranfverfe wrinkles of 

 the trunk. The vermes refemble the laft mentioned larva: ; 

 but they undergo no change of form. 



The largeft have the body divided into diftinft rings : a 

 knotted nervous cord is found in their interior. Thofe 

 which live in water, breathe by membranous or tufted 

 branchiae, like many aquatic larvae. Others have along the 

 fides of their body ftigmata precifely fimilar to the openings 

 of the trachese in infefts. The organs of motion, in feveral 

 inftances, are ftiff^ briftles or fpines. Others crawl by fuc- 

 ceflively wrinkling or contrafting the different parts of the 

 body. Some have even antennas. In fliort, we cannot af- 

 fign any general charafter, drawn either from external form 

 or internal ftrufture, which would be fufBcient, in all cafes, 

 to diftinguifli worms from the larvae of infefts. 



Moft worms inhabit the interior of other animals, as the 

 larvae of fome infefts do : others live in the earth or water. 

 Some of the latter conftruft folid habitations, either by 

 agglutinating foreign fubftances, or by pouring out a cal- 

 careous matter, like that of the teftaceous mollufca. But 

 the ftiells of worms may always be diftinguiftied from thofe 

 of the mollufca, becaufe they are always either ftraight or 

 tortuous tubes, never regularly fpiral, or an expanded cone, 

 and more particularly becaufe the animal is never attached, 

 which it is almoft invariably in the cafe of the mollufca. 



This clafs of vermes has been divided by Lamarck into 

 two; namely, worms, and annular animals (annelides). His 

 clafs of worms contains the inteftinal worms, and fome 

 others, whofe organization is equally imperfcft. The ani- 

 mals included in this clafs have a foft body more or lefs elon- 

 gated, 



