410 



MUSEUM OF ANIMATED NATURE. 



[Phytozoa. 



«h»Il proceed to a more definite review of the 

 cla>scs into which the »ubl<ingdom Acrila is divided. 



CIJVSS POUIFEKA 

 (SroNCics).-\Vho that takes up a piece of sponsre 

 would regard it as an animal production? yet such 

 is it renardcd by most zoologists. Sponge however, 

 as ordinarily seen, is not the animal itself, but the 

 framework upon which the living mass is sustained. 

 In its original state it was invested with a tilmy 

 coaling of transparent granular gelatine, every fibre, 

 every filament being covered, as if indeed it had 

 been dipped in jelly. It is this gelatine, replete 

 with lrans|)arent granules, which nally constitutes 

 the animal, and it is this that produces the cellular 

 framework called sponge. 



It is in the seas of the warmer latitudes that 

 apongesare principally tobe found; theretheyluxuri- 

 ale, attaining to the largest dimensions, and display- 

 ing the most varied forms. Fixed to the rock, they 

 fe.-toon the deep sea caves, line the walls with sub- 

 marine grottoes, and hang like fantastic pendants 

 from the roof; some like inverted vases, some like 

 fans, some like intertwisted branches. 



The common sponge of the Mediterranean was 

 well known to the ancients, and applied to the 

 same purposes as at present. The London maikel 

 is supplied from several quaiters, and distinct species 

 are in use, varying in their quality. If we take a 

 portion and examine it, wo shall find it made up of a 

 maze of elastic horny fibres crossing each other in all 

 -directions, and forming a cellular mass permeated 

 by innumerable pores, which, when the sponge is 

 dipped in water, absorbs the fluid by capillary 

 attraction, liesidcs these minute pores we find 

 lari^e and definite canals opening on its surface and 

 which traverse its substance. Now, in its natural 

 condition, invested with living gelatine, the spongre 

 is perpetually imbibing sea-water through the 

 pores, which saturates the whole mass; this is 

 again expelled in streams through the canals, and 

 thus a constant circulation is maintained. This is 

 the amount of our knowledge ri?apecting the aiija- 

 tion and nutrition of the sponge. It is indeed pro- 

 bable that by some process of absoption the sponge 

 takes up and incorporates nutritive matter; but 

 how the circulation of the sea-water is effected is 

 -still a mysteiy. It has been said by Lamarck, 

 Lamouroiix and others, that sponges when touched 

 exhibit slight tremulous or contractile movements ; 

 but later observers, as Dr. Grant, MM. Audouin 

 and Milne Edwards, asseit the contrary, and affirm 

 that no wounds or lacerations elicit the slightest 

 tremor in the living gelatine. There are moreover 

 no vibiatile cilia for the production of currents ; 

 and consequently by what agency (his palpable 

 circulation is effected has yet to be demonstrated. 

 As every part of a sponge is similarly organized, 

 and cariies on the same functions, it will hardly 

 .surprise us to leam that if divided into portions 

 •each piece becomes an independent being, yet it 

 is not in this manner that it multiplies. The sponge 

 is gemmiparous ; it gives birth to gemmules, or little 

 oval granules, the rudiments of future sponges. At 

 ceitain seasons of the year the canals traversing 

 the sponge are found to have their gelatinous 

 lining studded with little yellow buds sprouting 

 from it ; these increase and at length become de- 

 tached, and are carried out by the stream of water. 

 Strange to say, these gemmules appear to be more 

 highly organized than their parent. Their figure is 

 egg-shaped, and their larger extremity is covered 

 with numerous vibratile cilia, which are rapidly 

 agitated, producing currents in the surrounding 

 water, and propelling them along. Thus they 

 swim, free and active, to a considerable distance, 

 till a suitable locality offers for their settlement ; 

 they then attach themselves, never to remove ; the 

 ■cilia disappear ; they begin to grow, assuming their 

 specific form, develop their horny or silicious 

 framework, and in turn give origin to other pro- 

 genies. The wisdom of this arrangement is very 

 evident : the sponge affects calm and tranquil 

 spots, and were the myriads of gemmules to 

 become fixed at once, on exclusion from the 

 parent, the spot would be grown up with sponges, 

 and the distribution of the species throughout the 

 sea would depend upon mere casualties. 



The fibrous struction of sponge may be considered 

 as the rude skeleton of the living animal ; and the 

 characters of this framework vary greatly in different 

 species. Those of the sponge in ordinary use are too 

 well known to be detailed, but in many this frame- 

 work consists of a firm inflexible tissue of interwoven 

 filaments, which are tubular; the living gelatine is 

 also firmer, and not only exhibits bands of a more 

 tenacious or cartilaginous consistence than ordinary, 

 but is more or less replete with minute crystallized 

 spicula, generally fusiform, sometimes three-rayed. 

 Multitudes of the spicula are placed around the 

 internal walls of the canals which they line. They 

 may be obtained by washing a sponge of which the 

 animal matter is decomposing, or by fusing it 



it before the blowpipe. They are found to consist of 

 I silica, orflint, and, minute as they are, are capable of 

 scratching glass. In the genus Tethya the frame- 

 work consists almost entirely of silicious spicula 

 or filaments, and quantities are found in the a.shes 

 of Spongilla fluviatilis and other species : a minute 

 portion of silica has been found in the ashes of the 

 common sponge ; and it appears that in proportion 

 to the density of the fibres of the sponge is the 

 proportion of silica entering into their chemical 

 composition. In elastic sponges the fibres consist 

 principally of animal matter. Fig. 3812 represents 

 —1, the Spongia oculata, of the British coast : in 

 this the pores are seen and the canals from which 

 the currents are issuing; 2, the anastomosing horny 

 fibres of common sponge; 3, a silicious spiculum 

 of Spongia papillaris; 4, of Spongia cinerea ; 5, of 

 Spongia panirea; 6, a calcareous spiculum of 

 Spongia coiupressa; 7, transveree section of a 

 canal of Sponsiia papillaris, to show the structure, 

 and the geniniule passing-along the canal : 8, gem- 

 mule of Spongia panicea; 9, the same, seen at its 

 larger end, with a circle of water produced by 

 ciliary action ; 10. young Spongia papillaris com- 

 mencing to grow from a gemmule attached to the 

 rock. 



Sponge.', like plants, while retaining their specific 

 characteis, luxuriate in individual differences; the 

 geneial Ibrni, the general aspect of each species is 

 preserved, but as no two plants precisely correspond 

 in the number of branches or of leaves, so do these 

 in like manner vary as accidental circumstances 

 may determine. When torn or injured, sponges 

 repair the wound; we have several specimens that 

 have been lacerated, and show distinctly the new 

 matter by which the hiatus has been filled up. 



Fossil sponges are numerous ; they are found in 

 the oolite, in the green-sand formation, and in a si- 

 licious state in the chalk. 



CLASS PHYTOZOA 

 (Anthoina, Ehrenberg ; Polypifera, Grant ; Zoo- 

 phytes of older authors). 



ras.sing from the non-irritable sponges, we advance 

 to a class interesting from the nature of the sub- 

 jects it comprehends, and from their varied forms 

 and elegant appearance. Many indeed, at a first 

 view, so closely resemble delicate sea-weeds, that we 

 are not surprised to find them considered as such 

 by persons who have collected them on the shore, 

 where they may be observed, some attached to shells, 

 some to pebbles or stones, and others to the fronds 

 of fuci. Their true characters indeed have been but 

 recently understood, and their first elucidation is 

 due to John Ellis, F.U.S., whose paper on the His- 

 tory of Coialiines and other marine product ions found 

 on the coasts of Great Britain and Ireland was read 

 before the Royal Society, in June, 1754. 



Though on our coasts many beautiful species of 

 the more plant-like species exist, as Thuiaria, Cam- 

 panulaiia, and Sertularia, it is in the warmer lati- 

 tudes of the ocean that the Phytozoa, or Polypifera, 

 display their wonderful variety of forms, from fans 

 of network, or streamers, bending like osiers before 

 the waves, to coials with chaliced flowers, and Ma- 

 drepores, which encrust rocks, form reefs dangerous 

 to the navigator, or rise in islets covered with inter- 

 tropical vegetation. 



In order to convey a clear idea of these polype- 

 bearing animals, let us begin with the simplest of 

 their forms. There is in fresh water a minute ge- 

 latinous creature termed Hydra, of which several 

 species are known (as H. viridis, H. vulgaris, H. 

 fu.sca, &c.). These animals are of slender figure, 

 with an infernal cavity, and an oral orifice surrounded 

 by moveable arms or tentacles. They possess the 

 most extraordinary powers of contraction and elon- 

 gation, and are highly carnivorous ; they attach 

 themselves by means of a caudal sucker to the leaves 

 of aquatic plants, and spread abroad their arms in 

 quest of prey, which they drag to the mouth and 

 engulf. No nerves or muscular fibres have been 

 detected, but the gelatine composini? the body is 

 replete with minute granules. The Hydra is tena- 

 cious of life, and when cut asunder, each part be- 

 coiufts a perfect and independent being : yet though 

 apparently insensible to pain, it appears to appre- 

 ciate the presence of light ; and its tentacles doubt- 

 less feel the prey round which they cling. The 

 Hydra is free, and moves about over the surface of 

 leaves, or swims in the water with the tentacles 

 downwards, the caudal sucker acting as a float; 

 when alarmed, it contracts its tentacles and shrinks 

 into the form of a small globule, easily escaping ob- 

 servation. These minute creatures are not uncom- 

 mon in clear ponds or slow rivers. In the Hydra we 

 have an example of a free, independent, gelatinous 

 polype of the simplest structure, the digestive appa- 

 ratus being a simple excavation of its substance ; it 

 is itself a digestive saccul us; a stomach fringed with 

 tentacles for its own supply. 



Now suppose one of these should expand greatly 

 and deposit within itself a calcareous substance, act- 



[ mg as a sort of rude skeleton, invested with gelati- 

 nous film, much as we have seen in the sponge, and 

 become, though not fixed, incapable of locomotion. 

 Such a being we have in the Fungia, one of the 

 Madrephyllioea of De Biainville ; the stony axis or 

 polypary of which has the upper surface adorned 

 with radiating plates, rendering it not unlike a 

 mushroom. These animals are Ibund in the Indian 

 Seas, and lie loose and unattached upon the soft 

 sand at the bottom of the water. The gelatinous 

 investment is contiactile, and reproduction takes 



fdacc by buds or gemmules, which grow, become at 

 ength detached, and are carried away by the w aves. 

 Fig. 3813 shows Fungia patellaris : n, the upiier 

 face, b, the lower ; the middle figure is a side 

 view, the other shows the section of a portion. 



Here then we have an example of an independent 

 polype investing a radiated skeleton, though all the 

 species have not tentacles. In many, however, as 

 in Fungia actiniformis, they are numerous, and thick 

 on the upper disc, in the centre of which is the 

 mouth. 



Let us advance another step, and fancy a gela- 

 tinous extension, common to many polypes, united 

 as it were into one compound unity, and secreting 

 for the internal support, or skeleton, a branching 

 calcareous tree, with cells on the branches, in which 

 the polypes are lodged, and from which they may 

 protrude and expand their tentacles ; such we have 

 in branched madrepores, as Oculina, Dentipoia, 

 Millepora, &c. In other instances the gelatine may 

 secrete large calcareous masses for its support, with 

 polype cells variously arranged, as in AstiU'a, Mean- 

 drina, &c. In these instances the calcareous support 

 is firmly consolidated to the rock on which it is 

 based, and the polypes, often of most beautiful tints, 

 resemble thickly scattered flowers on a glistening 

 bank or silvery tree. We must not suppose, however, 

 that a solid calcareous axis is always deposited — on 

 the contrary, sometimes, as inGorgiona, we find the 

 axis horny and elastic ; in this case it is geneially in 

 form of a fan, or like a branch of the weeping-willow, 

 and, rooted on the rock, bends to waves. In these 

 instances there are no polype cells in the horny stems 

 or twigs, but only in the gelatinous bark, or cortical 

 substance which invests them, and in these do the 

 animal flowerets dwell. In other cases, as in the 

 Isis Hippuris, the stem is composed alternately of 

 joints of flexible horny matter, and of calcareous 

 substance, resembling interrupted beads of white. 

 This stem is clothed with the gelatinous bark, of 

 considerable thickness, in which are the polyparies, 

 or polype cells. 



So far we have described the general nature of 

 Phytozoa, in which the living gelatine, uniting mul- 

 titudes of animal flowerets or polypes, invests an 

 axis differing in form and substance. Let us, on 

 the contrary, now picture a number of polypes united 

 by threadlike films into onebeing, and these threads 

 cased within a tubular sheath of horn, which they 

 have secreted. Let us picture the whole as a tult 

 of delicate vegetation, a frondescent plant of tubu- 

 lar horn, with orifices or cups or bells bestudding 

 every branch, in which the polypes reside, and from 

 which they can protrude their contractile tentacles. 

 Such have we in the Serlularioe, compound tubular 

 Phytozoa, which we find rooted to stones and shells 

 in abundance on our own coast. 



There are, however, some Phytozoa which inhabit 

 calcareous tubes, and in some instances these tubes 

 are collected into masses of considerable extent, all 

 ranged in order, like reeds bound together, or the 

 pipes of an organ : they are open at one end, through 

 which the polypes, independent of each other, ex- 

 cept when they form the bands or stages which 

 unite the pipes together, protrude their flowerets. 

 Such is the beautiful Tubipoia musica, of a deep 

 red. 



Distinct ahke from the cortical and the tubular 

 Phytozoa are the Alcyonida;. In these there is 

 neither a calcareous axis nor a horny or calcareous 

 sheath; but a firm cartilaginous mass, with calca- 

 reous spicula dispersed through its substance, at 

 lea,st in some instances, is studded with hydra-like 

 polypes, each in its own cell, the cells being exca- 

 vated in the living gelatinousmass, to the nutriment 

 of which, as the common bond of union between 

 them, they all alike contribute. These may be called 

 compound cartilaginous Phytozoa. | 



A very strange form is represented by the Pen- , 

 natulise, or Sea-pens, of which Cuvier forms a distinct '' 

 group. Here we find a calcareous stem with lateral 

 branches disposed on each side, the whole bearing ■ 

 some resemblance to a quill-fealher ; along each ' 

 branch are cells, in which the polypes reside, and 

 these are united by a living filmy thread, sheathed 

 in the branches and shaft. The Pennalula; and Vir- 

 gularim are free, and carried about by the waves. 



Another form of Phytozoa is presented by the Ac- 

 tiniae, or Sea Anemonies, which are so abundant oil 

 the rocks along our shores, and to which they adhere 

 by their base, expanding their richly-tinted arms ia 

 quest of prey. Some species are unattached. AJ- 



