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STOMACH, BODY, ARMS, AND FINGERS OF PENTACRINITE. 331

Stomach.

The abdominal cavity or stomach, of the Pentacrinite, (Pl. 51, Fig. 2.,) is rarely preserved in a fossil state; it formed a funnel-shaped pouch, of considerable size, composed of a contractile membrane, covered externally with many hundred minute calcareous angular plates. At the apex of this funnel was a small aperture, forming the mouth, susceptible of elongation into a proboscis for taking in food.* The place of this organ is in the centre, of the body, surrounded by the arms.

Body, Arms, and Fingers.

The body of the Pentacrinite, between the summit of the column and the base of the arms, is small, and composed of the pelvis, and the costal, and scapular plates, (See Pl. 51. Pl. 52. Fig. 1. 3. and Pl. 53. Fig. 2. 6. E. F. H.) The arms and fingers are long and spreading, and have numerous joints, or tentacula; each joint is armed at its margin with a small tubercle or hook, (Pl. 53. Fig. 17.,) the form of which varies in every joint, to act as an organ of prehension; these arms and fingers, when expanded, must have formed a net of greater capacity than that of the Encrinites.t

We have seen that Parkinson calculates the number of bones in the Lily Encrinite to exceed twenty-six thousand.

• This unique specimen forms part of the splendid collection of James Johnson, Esq. of Bristol.

†The place of the Pentacrinites in the family Echinoderms, would lead us to expect to find minute pores on the internal surface of the fingers, analogous to those of the more obvious ambulacra of Echini; they were probably observed by Guettard, who speaks of orifices at the terminating points of the fingers and tentacula.

Lamarck also, describing his generic character of Encrinus, says: "The branches of the Umbel are furnished with Polypes, or suckers, disposed in rows."

The number of bones in the fingers and tentacula of the Briarean Pentacrinite amounts at least to a hundred thousand; if to these we add fifty thousand more for the ossicula of the side-arms, which is much too little, the total number of bones will exceed a hundred and fifty thousand. As each bone was furnished with at least two fasciculi of fibres, one for contraction, the other for expansion, we have a hundred and fifty thousand bones, and three hundred thousand fasciculi of fibres equivalent to muscles, in the body of a single Pentacrinite-an amount of muscular apparatus concerned in regulating the ossicula of the skeleton, infinitely exceeding any that has been yet observed throughout the entire animal creation.*

When we consider the profusion of care, and exquisite contrivance, that pervades the frame of every individual in this species of Pentacrinite, forming but one of many members, of the almost extinct family of Crinoïdeans—and when we add to this the amount of analogous mechanisms that characterize the other genera and species of this curious family, we are almost lost in astonishment, at the microscopic attention that has been paid to the welfare of creatures, holding so low a place among the inhabitants of the ancient deep; and we feel a no less irresistible conviction of the universal presence and eternal agency of Creative care, in the lower regions of organic life, than is forced upon us by the contemplation of those highest combinations of animal mechanism, which occur in that paragon of animal organization, the corporeal frame of Man.

* Tiedemann, in a monograph on Holothuria, Echini, and Asteriæ, states that the common Star-fish has more than three thousand little bones.

† A frequent repetition of the same parts is proof of the low place and comparative imperfection of the animal in which it occurs. The number of bones in the human body is but two hundred and forty-one, and that of the muscles two hundred and thirty-two pairs. South's Dissector's Manual.

SECTION II.

FOSSIL REMAINS OF POLYPES.

It was stated in our Chapter on Strata of the Transition Series, that some of their most abundant animal remains are fossil Corals or Polyparies. These were derived from an order of animals long considered to be allied to marine plants, and designated by the name of Zoophytes; they are usually fixed, like plants, to`all parts of the bottom of the sea in warm climates which are not too deep to be below the influence of solar heat and light, and in many species, send forth branches, assuming in some degree the form and aspect of vegetables. These coralline bodies are the production of Polypes, nearly allied to the common Actinia, or Sea Anemone of our own shores. See Pl. 54. Fig. 4. Some of them, e. g. the Caryophyllia, see Pl. 54. Figs. 9, 10. are solitary, each forming its own independent stem and support; others are gregarious, or confluent; living together on the same common base or Polypary, which is covered by a thin gelatinous substance, on the surface of which are scattered tentacula, corresponding with the stars on the surface of the coral, (see Pl. 54. Fig. 5.)

Le Sueur, who observed them in the West Indies, describes these Polypes, when expanded in calm weather at the bottom of the sea, as covering their stony receptacles with a continuous sheet of most brilliant colours.

The gelatinous bodies of these Polypes are furnished with the power of secreting carbonate of Lime, with which they form a basis of attachment, and cell of retreat. These calcareous cells not only endure beyond the life of the Polypes that secreted them, but approach so nearly to Limestone in their chemical composition, that at the death of the

Polype they remain permanently attached to the bottom Thus one generation establishes the basis whereon the next fixes its habitation, which is destined to form the foundation of a farther and cóntinual succession of similar constructions, until the mass, being at length raised to the surface of the sea, a limit is thereby put to its farther accumulation.

The tendency of Polypes to multiply in the waters of warm climates is so great, that the bottom of our tropical seas swarms with countless myriads of these little creatures, ever actively engaged in constructing their small but enduring habitations. Almost every submarine rock, and submarine volcanic cone, and ridge, within these latitudes, has become the nucleus and foundation of a colony of Polypes, chiefly belonging to the genera Madrepora, Astrea, Caryophyllia, meandrina, and Millepora. The calcareous secretion of these Polypes are accumulated into enormous banks or reefs of coral, sometimes extending to a length of many hundred miles; these continually rising to the surface in spots where they were unknown before, endanger the navigation of many parts of the tropical seas.*

If we look to the office these Polypes perform in the present economy of nature, we find them acting as scavengers of the lowest class, perpetually employed in cleansing the waters of the sea from the impurities which escape even the smaller Crustacea; in the same manner as the Insect Tribes, in their various stages, are destined to find their food by devouring impurities caused by dead animal and vegetable matter upon the land.† The same system

* Interesting accounts of the extent and mode of formation of these Coral Reefs may be found in the voyages of Peron, Flinders, Kotzebue, and Beechy; and an admirable application of the facts connected with modern Corals to the illustration of geological phenomena has been made by Dr. Kidd in his Geological Essay, and by Mr. Lyell in his Principles of Geology, 3d edit. vol. iii.

† Mr. De la Beche observed that the Polypes of the Caryophyllia Smithii (Pl. 54, Figs. 9, 10, 11,) devoured portions of the flesh of

appears to have prevailed from the first commencement of life in the most ancient seas, throughout that long series of ages whose duration is attested by the varied succession of animal and vegetable exuvia, which are buried in the strata of the earth. In all these strata the calcareous habitations of such minute and apparently unimportant creatures as Polypes, have formed large and permanent additions to the solid materials of the globe, and afford a striking example of the influence of animal life upon the mineral condition of the earth.*

If there be one thing more surprising than another in the investigation of natural phenomena, it is perhaps the infinite extent and vast importance of things apparently little and insignificant. When we descry an insect, smaller than a mite, moving with agility across the paper on which we write, we feel as incapable of forming any distinct conception of the minutia of the muscular fibres, which effect these movements, and of the still smaller vessels by which they are nourished, as we are of fully apprehending the magni

fishes, and also small Crustacea, with which he fed several individuals at Torquay, seizing them with their tentacula, and digesting them within the central sac which forms their stomach.

* Among the Corals of the Transition Series are many existing genera, and Mr. De la Beche has justly remarked (Manual of Geology, p. 454) that wherever there is an accumulation of Polypifers such as would justify the appellation of coral banks or reefs, the genera Astrea and Caryophyllia are present; genera which are among architects of coral reefs in the present

seas.

A large part of the Limestone called Coral Rag, which forms the elevated plains of Bullington and Cunmer, and the hills of Wytham, on three sides of the valley of Oxford, is filled with continuous beds and ledges of petrified corals of many species, still retaining the position in which they grow at the bottom of an ancient sea; as coral banks, are now forming in the intertropical regions of the present ocean.

The same fossil coralline strata extend through the calcareous hills of the N. W. of Berkshire, and N. of Wilts; and again recur in equal or still greater force in Yorkshire, in the lofty summits on the W. and S. W. of Scarborough.

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