THE POLYPUS. 



565 





those of the sea often shoot forth a stalk of a 

 hundred. It is so between the polypi of both 

 elements. Those of the sea are found from 

 two feet in length to three or four, and Pliny 



the application of corrosive chemical agents. He has 

 discovered the true nature of the currents of fluid issuing 

 at different points, which he thus graphically describes : 

 " I put a small branch of the spongia coalita, with some 

 sea-water, into a watch-glass, under the microscope, and, 

 on reflecting the light of a candle through the fluid, I 

 soon perceived that there was some intestine motion in 

 the opaque particles floating through the water. On 

 moving the watch-glass, so as to bring one of the aper- 

 tures on the side of the sponge fully into view, I beheld, 

 for the first time, the splendid spectacle of this living 

 fountain, vomiting forth, from a circular cavity, an im- 

 petuous torrent of liquid matter, and hurling along, in 

 rapid succession, opaque masses, which it strewed every 

 where around. The beauty and novelty of such a scene 

 in the animal kingdom, long arrested my attention, but 

 after twenty-five minutes of constant observation, I was 

 obliged to withdraw my eye from fatigue, without having 

 seen the torrent for one instant change its direction, or 

 diminish, in the slightest degree, the rapidity of its 

 course." It thus appears that the large orifices on the 

 surface of a living sponge, are destined for the discharge 

 of a constant stream of water from tlie interior of the 

 body. We have attempted to represent the particles 

 thrown out by these currents in f. 70. These currents, 

 issuing from the larger orifices, are best seen by placing 

 the living animal in a shallow vessel of sea-water, and 

 strewing a little powdered chalk over the surface, the 

 motions of which render the current very sensible to the 

 naked eye. It is by the myriads of minute pores, which 

 exist in every part of the surface, that this water enters, 

 conveying with it the materials necessary for the sub- 

 sistence of the animal. These pores conduct the fluid 

 into the interior, where, after percolating through the 

 numerous channels of communication which pervade the 

 substance of the body, it is collected into wider passages, 

 terminating in the focal orifices above described, and is 

 finally discharged. The mechanism by which these cur- 

 rents are produced, is involved in much obscurity. 



The genus vorticella is constituted of a small tribe of 

 animals which differ from the polypi in one particular, 

 namely, that of being destitute of tentacula, and having 

 cilia only, surrounding the margin of a bell-shaped body, 

 which is mounted upon a long, slender peduncle. The 

 animals of this genus are always attached to some extra- 

 neous body by this footstalk, as represented in vorticella 

 polypina, pi. 30, f. 75, but have the power of moving 

 about in all direction?, to the extent of the range of the 

 footstalk. Currents are, as usual, excited by the vibra- 

 tions of the cilia, and these are the efficient instruments 

 of progressive motion. The ordinary position of the 

 peduncle of the vorticella is spiral, but it can extend it 

 quite in a straight line when in search of food ; but it 

 suddenly retreats from danger, by resuming the spiral 

 folds of its peduncle. 



Lamarck arranges the polypi under five orders, with 

 the following characters : 



I. POLYPI NATANTKS. Polypi provided with tenta- 

 cula, united in a common fleshy mass, placed on an axis, 

 free, and floating: in the water. 



II. POLYPI TUBIFEBI. Tentaculated polypi united 

 in a common fleshy body, without any solid axis, and 

 covered with tubiform cylinders. 



III. POLYPI VAGINATI. Polypi with tentacula, always 

 fi xcd in an inorganic covering, and forming in general 

 compound animals. 



IV. POLYPI DKNUDATI. Tentaculated polypi not 

 forming a common .envelop, fixed either constantly or 

 spontaneously. 



V. POLYPI CILIATI. Polypi without any tentacula; 



has even described one, the arms of which 

 were no less than thirty feet long. Those in 

 fresh waters, however, are comparatively mi- 

 nute ; at their utmost size seldom above three 



but instead of them, vibratile cilise, at or near the 

 mouth. 



ORD?:R i. POLYPI NATANTES. 



Polypi united in a common fleshy body, or congre- 

 gated mass, free, elongated, enveloping an inorganic 

 axis, cartilaginous, osseous, or stony; eaeli polypus pro 

 vided with tentacula placed around the mouth, and ra- 

 diating. The animals of this order are congregated on 

 a common body, in which they all participate, while 

 each appears to enjoy a separate existence, and distinct 

 powers of volition. The common body has the appear- 

 ance of a naked fleshy mass, with the polypi protruding 

 from its surface, and in the centre is placed an inorganic 

 axis resulting from some deposition of the animals, in- 

 the same manner as the outer covering in the other or- 

 ders. Some of these compound animals float freely in 

 the water, and others remain at the bottom in the mud 

 or sand. Many of them diffuse a vivid phosphorescent) 

 light. Umbell'ularia. G reenlandica, pi. 30, f. 13. Body 

 free, consisting of a long simple stem, with a bony in ar- 

 ticulated axis, enveloped by a fleshy membrane. In- 

 habits the Northern ocean. Vtryutoria ; body free, fili- 

 form or linear, greatly elongated'. Inhabits the North- 

 ern ocean. Renilla ; body free, depressed, kidney- 

 shaped, polypi provided with six rays each. Pemiatula 

 phosphorea,p\. 30, f. 14. Body free, fleshy, pen inform, 

 polypi with radiated tentacula. Fig. 65 represents- 

 some of the polypes greatly magnified. Inhabits the 

 British seas. Funiculina; body free, filiform, very sim- 

 ple, long, fleshy, and provided with warts. Inhabits- 

 the American ocean. Veretillum ; body free, fleshy, sim- 

 ple, cylindrical, polypiferous above, and with the base 

 naked. 



ORDER II. POLYPI TUBIFERL 



Polypi united in a common fleshy body, either simple, 

 lobed, or ramified, and constantly fixed at its base, des- 

 titute of any solid internal axis ; surface entirely or in 

 part covered with tubiform cylinders, rarely retractile; 

 mouth terminal, provided with eight pectinated tenta- 

 cula. The tubiferous polypi always exist in the form 

 of a fleshy subgelatinous body, invariably fixed by their 

 base. They are more or less simple, convex, lobed, or 

 slightly ramified. The upper part of the surface of their 

 body is covered with a vast number of small tubiform 

 movable cylinders; having at then 1 summit a roundish 

 sub-octagonal mouth surrounded by eight pectinated 

 tentacula. Lobularia dit/itata, pi. 30, f. 15. Common 

 body of a fleshy consistence, elevated upon the base. 

 Inhabits the coast of Europe. Fig. 16 is a magnified 

 view of a portion of this species. Ciiona; of a fleshy, ir- 

 ritable substance, provided with siliceous spicula, gen- 

 erally embedded in the cavities of shells. Inhabits 

 em 

 wit 



branched stems. Inhabits the coasts of the Red sea. 

 Xenia; the common body provided with thick, some- 

 what short, naked stems, emanating from the base, and 

 divided at their summit. Anthelia ; common body 

 spread out in a thin plate, or depressed over marine 

 substances. Inhabits the shores of the Red sea. 



ORDER III. POLYPI VAGINATI. 



Each individual polype tentaculated, constantly fixed 

 in an inorganic body, or sheath, which completely enve- 

 lops them, and forming in general compound animals, 

 This is the most extensive class of polypi, and is divided 

 into seven sections. The animals are very delicate, 

 transparent, and extremely contractile, usually fixed in 

 an inorganic body of their own formation. This calcare- 

 ous mass is increased in size with every successive gen- 

 eration; and these, in the course of time, accumulate to 

 such a size, that they raise islands in the midst of the 

 ocean. The cells are short, long, or tubular, the orifice 



mpty oyster shells on the British coasts. Ammothea ; 

 ith the common body divided into many short and 



