Polyp

“ To become a polyp, the actinula (fig. 3, A) becomes attached to some firm object by the pole farthest from the mouth, and its growth preponderates in the direction of the principal axis, that is to say, the axis passing through the mouth (fig. 3, a-b) . As a result the body becomes columnar in form (fig. 3, B) , and without further change passes into the characteristic polyp-form (see Polyp) . ”

“ In the centre of the disc is the mouth, a simple opening, a mere hole in the top of a sac.
[86] Our polyp, or anemone, has no organs of locomotion, no organs of sight, taste or hearing, indeed no brain. It has at any rate the rudiments of a nervous and muscular system, for it is able to move its tentacles all towards that one which has captured prey and assist it in conveying the food to the mouth. ”

“ It is an almost universal attribute of polyps to possess the power of “reproducing themselves non-sexually by the method of budding. This mode of reproduction may be combined with sexual reproductiveness, or may be the sole method by which the polyp produces offspring, in which case the polyp is entirely without sexual organs. In many cases the buds formed do not separate from the parent but remain in continuity with it, thus forming colonies or stocks, which may reach a great size and contain a vast number of individuals. ”

“ The polyp cells are oval, placed just under the skin, and are the terminating points of certain long canals which traverse the whole polypidom. The polyps, which are distributed over the whole surface, can withdraw into the cavities; they are, besides, of an extremely vital sensibility: the least shock impresses itself on the tentacula, the impulse of a wave even producing contraction; in response, the animal, which is well developed, sallies out perceptibly, but immediately retires again to hide itself in the cell. ”

“ The polyp may be solitary, but more usually produces polyps by budding and forms a polyp-colony. The polyp usually has the body distinctly divisible into hydranth, hydrocaulus and hydrorhiza, and is usually clothed in a perisarc. The medusae may be set free or may remain attached to the polyp-colony and degenerate into a gonophore. When fully developed the medusa is characterized by the sense organs being composed entirely of ectoderm, developed independently of the tentacles, and innervated from the sub-umbral nerve-ring. ”

“ The buds may all become detached after a time and give rise to separate and independent individuals, as in the common Hydra, in which only polyp-individuals are produced and sexual elements are developed upon the polyps themselves; or, on the other hand, the polyp-individuals produced by budding may remain permanently in connexion with the parent polyp, in which case sexual elements are never developed on polyp-individuals but only on medusa-individuals, and a true colony is formed. ”

“ Polyorama, pol-i-ō-ra′ma, n. an optical apparatus presenting many views.
Polyp, Polype, pol′ip, n. a name usually applied to an animal like the fresh-water hydra, having a tubular body, and a wreath of many tentacles round the mouth: something with many feet or roots: a pedunculated tumour attached to the surface of a mucous membrane—in the nose, &c.—also Pol′ypus:—pl. Polypes (pol′ips) , Polypi (pol′i-pī) .—ns. Pol′ypary, the horny or chitonous outer covering of a colony of polyps; Pol′ypide, an individual zoöid of a polyzoarium or compound polyzoan ”

“ Thus the typical hydroid colony starts from a “founder” polyp, which in the vast majority of cases is fixed, but which may be floating, as in Nemopsis, Pelagohydra, &c. The founder-polyp usually produces by budding polyp-individuals, and these in their turn produce other buds. The polyps are all non-sexual individuals whose function is purely nutritive. After a time the polyps, or certain of them, produce by budding medusa-individuals, which sooner or later develop sexual elements ”

“ The Hertwigs when they discovered the endoderm-lamella showed on morphological grounds that polyp and medusa are independent types, each produced by modification in different directions of a more primitive type represented in development by the actinula-stage. If a polyp, such as Hydra, be regarded simply as a sessile actinula, we must certainly consider the polyp to be the older type, and it may be pointed out that in the Anthozoa only polyp-individuals occur. ”

“ In this sense, creatures extremely low in the intellectual scale may have conception. All that is required is that they should recognize the same experience again. A polyp would be a conceptual thinker if a feeling of 'Hollo! thingumbob again!' ever flitted through its mind. ”

“ An opening soon presents itself in the centre of this extremity, through which an internal cavity appears. Four little mammals have now appeared on the edge, which are elongated in the manner of arms. Others soon follow: these are the tentacles of a polyp: the young infusoria has become a polyp!
The polyp increases by buds and shoots, just like a strawberry [226] plant, which throws out its slender stems in all directions, covering all the neighbouring ground.
The young Medusa lives some time under this form. Then one of the polyps becomes enlarged and its form cylindrical. ”

“ By budding is understood the formation of a new individual from a fresh growth of undifferentiated material. It is convenient to distinguish buds that give rise to polyps from those that form medusae.
(a) The Polyp.—The buds that form polyps are very simple in mode of formation. Four stages may be distinguished; the first is a simple outgrowth of both layers, ectoderm and endoderm, containing a prolongation of the coelenteric cavity; in the second stage the tentacles grow out as secondary diverticula from the side of the first outgrowth ”

“ In case of many polyps all or some of the new individuals which arise by budding do not become polyps, but develop into medusæ or jellyfish, which separate from the fixed polyp and swim off through the water. ”

“ Upon the delicate branches we find little horny cups, each of which is the habitation of a tiny Polyp, furnished with a mouth and stomach, and with a circlet of slender arms to enable it to capture its prey. Other species are enclosed only in a soft membrane, but all rise from creeping roots. ”

“ Each petal carries on its edges a row of very slender transparent filaments, arranged like the teeth of a comb, which also arch downward, and greatly augment the beauty of the flower-like polyp.
Structurally, this polyp is closely allied to the common forms of the Sea Anemones; the most obvious peculiarity being, that a multitude are combined into one mass, with a common life animating the whole. [Pg 75] The fleshy mass is of a spongy texture, full of branching water-canals, and containing a multitude of calcareous spicula of characteristic forms. ”

“ The species are multiplied by a kind of vegetation, one or two, or even more young ones, emerging gradually from the sides of the parent animal; and these young ones are frequently again prolific before they drop off; so that it is no uncommon thing to see two or three generations at once on the same Polyp. But the most astonishing fact respecting this animal is, that if a Polyp be cut in pieces, it is not destroyed, but is multiplied by dissection. ”

“ It lives at a depth of about a hundred feet, and is often brought to the Zoological Station by the fishermen in large quantities. Its borrowed mollusc shell often bears a little polyp, Podocoryne carnea (Fig. 34) , which forms colonies of often [Pg 164] several hundred individuals, arising from a common root-work of stolons which covers the shell. The polyp colony is composed of different kinds of individuals or personæ, illustrating the principle of division of labour: it includes (1) nutritive persons (np) which possess a proboscis, mouth, and tentacles on their club-shaped bodies ”

“ The manner of dividing a Chrysipus differs, however, greatly from that of the Polypus; for whereas we are taught in that excellent treatise above-mentioned, that [4] 'If the body of a Polypus is cut into two parts transversely, each of those parts becomes a complete Polypus: on the very day of the operation, the first part, or anterior end of the Polypus, that is, the head, the mouth, and the arms: this part, I say, lengthens itself, it creeps, and eats.
'The second part, which has no head, gets one; a mouth forms itself at the anterior end; and shoots forth arms. ”

“ The worm, coming out of the mouth of the polype, forces it to enlarge itself considerably, especially if it comes out doubled up. When the polype is in this state, I take it gently out of the water, without disturbing anything, and place it on the edge of my hand, which is simply moistened, so that it [Pg 66] may not adhere too closely. I oblige it to contract more and more, and this also enlarges the stomach and mouth. ”

“ As a rule, the polyps are either male or female; but in stock-forming species individuals of the two sexes are often mixed. Monoxenia may be taken as the simplest type of the regularly radiate polyps; in all the different organs being repeated in regular rings round a central axis; the mouth also is circular. From this interesting account, drawn by Haeckel, of a simple polyp, it will be at once seen what kind of radiate animal it is that builds up the coral reefs. “No garden on earth can match the gardens of the sea that circle the northern part of Australia. ”

“ The simplest form of polype is that of a fleshy bag open at one end, surmounted by a circle of contractile threads or fingers called tentacles. The plate shows, on a very minute scale, at figs. 1, 3, and 6, several of these little polypiform bodies protruding from their cells. But the Hydra or Fresh-water Polype has no cell, and is quite unconnected with any root thread, or with other individuals of the same species. It is perfectly free, and so simple in its structure, that when the sac which forms its body is turned inside out it will continue to perform the functions of life as before. ”

“ Then each half-pipe becomes a whole one complete: a stomach is formed, in which nothing is wanting; and out of each half-mouth a whole one is formed also.
'I have seen all this done in less than an hour; and that the Polypus produced from each of those halves, at the end of that time, did not differ from the whole ones, except that it had fewer arms; but in a few days more grew out.
'I have cut a Polypus lengthways, between seven and eight in the morning; and between two and three in the afternoon, each of the parts has been able to eat a worm as long as itself. ”

“ When, from the process by which food is digested, we turn to the process by which it is seized, the same general truth faces us. The stinging and contractile power of a polype's tentacle, correspond to the sensitiveness and strength of the creatures serving it for prey. Unless that external change which brings one of these creatures in contact with the tentacle, were quickly followed by those internal changes which result in the coiling and drawing up of the tentacle, the polype would die of inanition. ”

“ A polype, feeding on minute annelids and crustaceans which, flitting through the water, come in contact with its tentacles, and limited to that quantity of prey which chance brings within its grasp, buds out young polypes which, either as a colony or as dispersed individuals, spread their tentacles through a larger space of water than the parent alone can; and by producing them, the parent better insures the continuance of its species than it would do if it went on slowly growing until its nutrition was nearly balanced by its waste, and then multiplied by gamogenesis. ”

“ Diocles, in the first book of his treatise on Wholesome Things, says—"The molluscous fish are calculated to give pleasure, and to excite the amorous propensities; especially the polypi (ὁι πολυποδες) ." And Aristotle relates that the polypus has eight feet, of which the two highest and the two lowest are the smallest, and those in the middle are the largest; and they have also two feelers, with which they bring their food to their mouth. And they have their eyes placed above their two upper feet; and their mouth and teeth are between their feet. ”

“ Coral Polyp. (Lacaze-Duthiers.)
The arms of the polyps are at times subject to violent agitation: the tentacula become much excited. If this excitement continues, the tentacula can be seen to fold and roll themselves up, as shown in Fig. 50. If we look at the expanded disk, we see that the eight tentacula attach themselves to the body, describing a space perfectly circular, in the middle of which rises a small mammal, the summit of which is occupied by a small slit like two rounded lips. This is the mouth of the polyps, the form being very variable, but well represented in Fig. ”

“ The progress of discovery, since Réaumur's time, has made us very completely acquainted with the structure and habits of all these polypes. We know that, among the sea-anemones and coral-forming animals, each polype has a mouth leading to a stomach, which is open at its inner end, and thus communicates freely with the general cavity of the body; that the tentacles placed round the mouth are hollow, and that they perform the part of arms in seizing and capturing prey. ”

“ Next day, the Polypus that resulted, eat. It has continued well these two months since the operation: it is grown, and has put forth young ones from each of the parts of which it was formed. The two foregoing experiments do not always succeed; it often happens, that the two parts will not join again.
'In order to comprehend the experiment I am now going to speak of, one should recollect, that the whole body of a Polypus forms only one pipe, a sort of gut, or pouch. ”