Geology and Mineralogy considered with reference to Natural Theology/Chapter 17
|←Chapter 16||Geology and Mineralogy considered with reference to Natural Theology by
Proofs of Design in the Structure of Fossil Radiated Animals, or Zoophytes.
The same difficulties which we have felt in selecting from other grand Divisions of the animal kingdom, subjects of comparison between the extinct and living forms of their respective Classes, Orders, and Families, embarrass our choice also from the last Division that remains for consideration. Volumes might be filled with descriptions of fossil species of those beautiful genera of Radiated Animals, whose living representatives crowd the waters of our present seas.
The result of all comparisons between the living and fossil species of these families would be, that the latter differ almost always in species, and often in genus, from those which actually exist; but that all are so similarly constructed on one and the same general Type, and show such perfect Unity of Design throughout the infinitely varied modifications, under which they now perform, and ever have performed the functions allotted to them, that we can find no explanation of such otherwise mysterious Uniformity, than by referring it to the agency of one and the same Creative Intelligence.
The animals that compose this highest Class in the grand division of Radiated animals, viz. Echinidans, Stelleridans, and Crinoïdeans, have, till lately, been considered as made up of many similar parts disposed like Rays around a common centre.
Mr. Agassiz has recently shown, (London and Edin. Phil. Mag. Nov. 1834, p. 369,) that they do not partake of this character, from which the division of radiated animals is named; but that their rays are dissimilar, and not always connected with a uniform centre; and that a bilateral symmetry, analogous to that of the more perfect classes of animals, exists throughout the families of Echini, Asteriæ, and Crinoidea.
ECHINIDIANS AND STELLERIDANS.
The History of the fossil species of Echinidans and Stelleridans has been most beautifully illustrated, in the plates of the Petrefacten of Prof. Goldfuss. Though derived from Strata of various degrees of high antiquity, they are for the most part referred by him to existing Genera.
The family of Echinidans appears to have extended through all Formations, from the Epoch of the Transition series to the present time.
No fossil Stelleridans have yet been noticed in strata more ancient than the Muschelkalk.
As the structure of the fossil species of both these families is so nearly identical with that of existing Echini, and Starfishes, I shall confine my observations respecting fossil animals in the class of Echinoderms to, a family which is of rare occurrence, excepting in a fossil state, and which seems to have prevailed most abundantly in the most ancient fossiliferous formations.
Among the fossil families of the Radiated division of animals, the Geologist discovers one whose living analogues are seldom seen, and whose vast numerical extent and extraordinary beauty entitle it to peculiar consideration.
Successions of strata, each many feet in thickness, and many miles in extent, are often half made up of the calcareous skeletons of Encrinites. The Entrochal Marble of Derbyshire, and the Black rock in the cliffs of Carboniferous limestone near Bristol, are well known examples of strata thus composed; and show how largely the bodies of Animals have occasionally contributed by their remains, to swell the Volume of materials that now compose the mineral world.
The fossil remains of this order have been long known by the name of Stone Lilies, or Encrinites, and have lately beenn classed under a separate order by the name of Crinoïdea;
This order comprehends many Genera and numerous Species, and is ranged by Cuvier after the Asteriæ, in the division Zoophytes. Nearly all these species appear to have been attached to the bottom of the Sea, or to floating extraneous bodies.
The two most remarkable Genera of this family have been long known to Naturalists by the names of Encrinite and Pentacrinite; the former (see Pl. 49, Fig. 1, and Pl. 47, Figs. 1. 2. 5.) most nearly resembling the external form of a Lily, placed on a circular stem; the latter (see Pl. 51, and Pl. 52, Fig. 1, 3,) retaining the general analogies of structure presented by the Encrinite, but, from the pentagonal form of its stem, denominated Pentacrinite. A third Genus, called Apiocrinites, or Pear Encrinite, (Pl. 47. Figs. 1, 2.) exhibits, on a larger scale, the component parts of bodies of this family; and has been placed by Mr. Miller at the head of his valuable work on the Crinoïdea, from which many of the following descriptions and illustrations will be collected.
Two existing species of recent animals throw much light on the nature of these fossil remains; viz. the Pentacrinus Caput Medusæ from the West Indies, represented at Pl. 52, Fig. 1, and, the Comatula fimbriata, figured in the first plate of Miller's Crinoïdea.
We will proceed to consider the mechanical provisions in the structure of two or three of the most important fossil species of this family, viewed in relation to their office as Zoophytes, destined to find their nourishment, by spreading their nets and moving their bodies through a limited space, from a fixed position at the bottom of the sea; or by employing the same instruments, either when floating singly through the water, or attached, like the modern Pentelasmis anatifera, to floating pieces of wood.
Although the representatives of Crinoïdeans in our modern seas are of rare occurrence, this family was of vast numerical importance among the earliest inhabitants of the ancient deep. The extensive range which it formerly occupied among the earliest inhabitants of our Planet, may be estimated from the fact, that the Crinoïdeans already discovered have been arranged in four divisions. comprising nine genera, most of them containing several species, and each individual exhibiting, in every one of its many thousand component little bones, a mechanism which shows them all to have formed parts of a well-contrived and delicate mechanical instrument; every part acting in due connexion with the rest, and all adjusted to each other with a view to the perfect performance of some peculiar function in the economy of each individual.
The joints, or little bones, of which the skeletons of all these animals were composed, resemble those of the starfish: their use, like that of the bony skeleton in vertebral animals, was to constitute the solid support of the whole body, to protect the viscera, and to form the foundation of a system of contractile fibres pervading the gelatinous integument with which all parts of the animal were invested.
The bony portions formed the great bulk of the animal, as they do in star-fishes. The calcareous matter of these little bones was probably secreted by a Periosteum, which in cases of accident, to which bodies so delicately constructed must have been much exposed in an element so stormy as the sea, seems to have had the power of depositing fresh matter to repair casual injuries. Mr. Miller's work abounds with examples of reparations of this kind in various fossil species of Crinoïdeans. Our Pl. 47, Fig. 2, a. represents a reparation near the upper portion of the stem of Apiocrinites Rotundus.
In the recent Pentacrinus (Pl. 52, Fig. 1,) one of the arms is under the process of being reproduced, as Crabs and Lobsters reproduce their lost claws and legs, and many lizards their tails and feet. The arms of star-fishes also, when broken oil; are in the same manner reproduced.
From these examples we see that the power of reproduction has been always strongest in the lowest orders of animals, and that the application of remedial forces has ever been duly proportioned to the liability to injury, resulting from the habits and condition of the creatures in which these forces are most powerfully developed.
As the best mode of explaining the general economy of the Crinoïdea, will be to examine in some detail the anatomy of a single species, I shall select, for this purpose, that which has formed the type- of the order, viz. the Encrinites moniliformis (sec Pl. 48, 49, 50.) Minute and full descriptions are given by Parkinson and Miller of this fossil, showing it to combine in its various organs a union of mechanical contrivances, which adapt each part to its peculiar functions in a manner infinitely surpassing the most perfect contrivances of human mechanism.
Mr. Parkinson states that after a careful examination he has ascertained that, independently of the number of pieces which may be contained in the vertebral column, and which, from its probable length, may be very numerous, the fossil skeleton of the superior part of the Lily Encrinite (Encrinites Moniliformis) consists of at least 26,000 pieces. See Pl. 50, Figs. 1, 2, 3, 4, &c.
Mr. Miller observes that this number would increase most surprisingly, were we to take into account the minute calcareous plates that are interwoven in the integument covering the abdominal cavity and inner surface of the fingers and tentacula.
We will first examine the contrivances in the joints, of the vertebral column, which adapted it for flexure in every direction, and then proceed to consider the arrangement of other parts of the body.
These joints are piled on each other like the masonry of a slender Gothic shaft, but, as a certain degree of flexibility was requisite at every articulation, and the amount of this flexure varied in different parts of the column, being least at the base and greatest at the summit, we find proportionate variations both in the external and internal form and dimensions of each part The varieties of form and contrivance which occur in the column of a single specie of Encrinite, may serve as an example of analogous arrangements in the columns of other species of the family of Crinoïdeans, (see Pl. 47. Figs. 1, 2, 5, and Pl. 49. Fig. 4 to Fig. 17.)
The name of Entrochi, or wheel stones, has with much propriety been applied to these insulated vertebræ. The perforations in the centre of these joints affording a facility for stringing them as beads, has caused them, in ancient times, to be used as rosaries. In the northern parts of England they still retain the appellation of St. Cuthbert's beads.
On a rock by Lindisfarn
Saint Cuthbert sits, and toils to frame
The sea-born beads, that bear his name.
Each of these presents a similar series of articulations, varying as we ascend upwards through the body of the animal, every joint being exactly adjusted, to give the requisite amount of flexibility and strength. From one extremity of the vertebral column to the other, and throughout the hands and fingers (see Pl. 47, figs. 1, 2, 3. and Pl. 50, figs. 1, 2, 3.,) the surface of each bone articulates with that adjacent to it, with the most perfect regularity and nicety of adjustment. So exact, and methodical is this arrangement, even to the extremity of its minutest tentacula, that it is just as improbable, that the metals which compose the wheels of a chronometer should for themselves have calculated and arranged the form and number of the teeth of each respective wheel, and that these wheels should have placed themselves in the precise position, fitted to attain the end resulting from the combined action of them all, as for the successive hundreds and thousands of little bones that compose an Encrinite, to have arranged themselves, in a position subordinate to the end produced by the combined effect of their united Mechanism; each acting its peculiar part in harmonious subordination to the rest, and all conjointly producing a result which no single series of them acting separately, could possibly have effected.
In Pl. 50 I have selected from Goldfuss, Parkinson, and Miller, details of the structure of the body and upper extremities of Encrinites Moniliformis, or Lily Encrinite, in which the component parts are indicated by letters, explained in the annexed note; and I must refer my readers to these authors for minute descriptions of the individual forms and uses of each successive series of plates.
From the subjoined analysis of the component portions of the body of the E. Moniliformis, we see that it may be resolved into four series of plates each composed of five pieces, and bearing a distant analogy to those parts in the organization of superior animals from which they have been denominated. A similar system of plates, varying in number and holding the same place between the column and the arms of the animal, may be traced through each species of the family of Crinoïdeans. The details of all these specific variations are beautifully illustrated by Mr. Miller, to whose excellent work I must again refer those who are inclined to follow him, through his highly philosophical analysis of the structure of this curious family of fossil animals.
From the details I have thus selected from the best authorities, with a view to illustrate the most important parts that enter into the organization of the family of Encrinites, it is obvious that similar investigations might be carried to an almost endless extent by examining the peculiarities of each part throughout their numerous species. We may judge of the degree, to which the individuals of these species multiplied among the first inhabitants of the sea, from the countless myriads of their petrified remains which fill so many Limestone beds of the Transition Formations, and compose vast strata of Entrochal marble, extending over large tracts of country in Northern Europe and North America. The substance of this marble is often almost as entirely made up of the petrified bones of Encrinites, as a corn-rick is composed of straws. Man applies it to construct his palace and adorn his sepulchre, but there are few who know, and fewer still who duly appreciate the surprising fact, that much of this marble is composed of the skeletons of millions of organized beings, once endowed with life, and susceptible of enjoyment, which after performing the part that was for a while assigned to them in living nature, have contributed their remains towards the composition of the mountain masses of the Earth.
Of more than thirty species of Crinoïdeans that prevailed to such enormous extent in the Transition period, nearly all became extinct before the deposition of the Lias, and only one presents the angular column of the Pentacrinite; with this one exception, pent angular columns first began to abound among the Crinoïdeans at the commencement of the Lias, and have from thence extended onwards into our present seas. Their several species and even genera are also limited in their extent; e. g. the great Lily Encrinite (E. moniliformis) is peculiar to the Muschelkalk, and the Pear Encrinite to the middle region of the Oolitic formation.
The Physiological history of the family of Encrinites is very important; their species were numerous among the most ancient orders of created beings, and in this early state their construction exhibits at least an equal if not a higher degree of perfection than is retained in the existing Pentacrinites; and although the place, which, as Zoophytes, they occupied in the animal kingdom, was low, yet they were constructed with a perfect adaptation to that low estate, and in this primeval perfection they afford another example at variance with the doctrine of the progression of animal life from simple rudiments through a series of gradually improving and more perfect forms, to its fullest development in existing species. Thus, a comparison of one of the early forms of the Genus Pentacrinite; viz. the Briarean Pentacrinite of the Lias, (Pl. 51 and Pl. 52, Fig. 3. and Pl. 53) with the fossil species of more recent formations, and with the existing Pentacrinus Caput Medusæ from the Caribbean Sea, Pl. 52, Fig. 1, shows in the organization of this very ancient species an equal degree of perfection, and a more elaborate combination of analogous organs, than occurs in any other fossil species of more recent date, or in its living representative.
The history of these fossil bodies, that abound in the lower strata of the Oolite formation, and especially in the Lias, has been much illustrated by the discovery of two living forms of the same Genus, viz. the Pentacrinus Caput Medusæ, (Pl. 52, Fig. 1,) and Pentacrinus Europaeus, Pl. 52, Figs. 2. 2'. Of the first of these a few specimens only have been brought up from the bottom of deep seas in the West Indies; having their lower extremities broken, as if torn from a firm attachment to the bottom. The Pentacrinus Europaeus. (see Pl. 52, Figs. 2. 2',) is found attached to various kinds of Sertularia and Flustracea in the Cove of Cork, and other parts of the coast of Ireland.
It appears that Pentacrinites are allied to the existing family of star-fishes, and approach most nearly to the Comatula; (see Miller's Crinoïdea, Pl. 1, and p. 127:) the bony skeleton constitutes by far the largest portion of these animals, In the living species this bony framework is invested with a gelatinous membrane, accompanied by a muscular system, regulating the movements of every bone. Although, in the fossil species, these softer part shave perished, yet an apparatus for muscular attachment exists on each individual bone.
The calcareous joints which compose the fingers of the P. Europasus, together with their tentacula, are capable of contraction and expansion in every direction; at one time spreading outwards, like the Petals of an open flower (Pl. 52, Fig. 2,) and at another rolled inwards over the mouth, like an unexpanded bud; the office of these organs is to seize and convey to the mouth its destined food. Thus the habits of living animals illustrate the movements and manner of life of the numerous extinct fossil members of this great family, and afford an example of the validity of the mode of argument, to which we are obliged to have recourse in the consideration of extinct species of organic remains. In this process we argue backwards, and from the mechanical arrangements that pervade the solid portions of fossil skeletons, infer the nature and functions of the muscles by which motion was imparted to each bone.
I shall select from the many fossil species of the Genus Pentacrinite, that, which from the extraordinary number of auxiliary side-arms, placed along its column, has been called the Briarean Pentacrinite, and of which our figures (Pl. 51. Figs. 1, 2.; Pl. 52. Fig. 3.; and Pl. 53.) will give a more accurate idea than can be conveyed by verbal descriptions.
The upper part of the vertebral column of Pentacrinites is constructed on principles analogous to those already described in the upper part of the column of the Encrinite.
All the joints of the column, when seen transversely, present various modifications of pentagonal star-like forms; hence their name of Asteriæ, or star-stones.
These transverse surfaces are variously covered with a succession of teeth, set at minute intervals from one another, and locking into the interstices between corresponding teeth on the surface of the next vertebrae, they are so disposed as to admit of flexure in all directions, without risk of dislocation.
As the base or root of Pentacrinites was usually fixed to the bottom of the sea, or to some extraneous floating body, the flexibility of the jointed column, which forms the stem, was subservient to the double office, first, of varying, in every direction, the position of the body and arms in search of food, and secondly, of yielding, with facility, to the course of the current, or fury of the storm, swinging, like a vessel held by her cable, with equal ease in all directions around her moorings.
The Root of the Briarean Pentacrinite was probably slight, and capable of being withdrawn from its attachment. The absence of any large solid Secretious, like those of the Pear Encrinite, by which this Pentacrinite could have been fixed permanently to the bottom, and the further fact of its being frequently found in contact with masses of drifted wood converted into jet (Pl. 52, Fig. 3.,) leads us to infer that the, Briarean Pentacrinite was a locomotive animal, having the power of attaching itself temporarily either to extraneous Boating bodies, or to rocks at the bottom of the sea, either by its side arms, or by a movable articulated small root.
The Side-Arms become gradually smaller towards the upper extremity of the column. In the P. Briareus (Pl. 52, Fig. 3. and Pl. 53, Fig. 1. and 3.) these amount to nearly a thousand in number. The numerous side-arms of the Briarean Pentacrinite, when expanded, would act as auxiliary nets so retain the prey of the animal, and also serve as hold-fasts to assist it in adhering to the bottom, or to extraneous bodies. In agitated water they would close and fold themselves along the column, in a position which would expose the least possible surface to the element, and, together with the column and arms, would yield to the direction of the current.
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. l7.,) 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.
We have seen that Parkinson calculates the number of bones in the Lily Encrinite to exceed twenty-six thousand. The number of bones in the lingers 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.
FOSSIL REMAINS OF POLYPES.
The 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 further and continual succession of similar constructions, until the mass, being at length raised to the surface of the sea, a limit is thereby put to its further 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 secretions 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 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 exuviæ, 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 minutiae 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 magnitude of the universe. We are more perplexed in attempting to comprehend the organization of the minutest Infusoria, than that of a whale; and one of the last conclusions at which we arrive, is a conviction that the greatest and most important operations of nature are conducted by the; agency of atoms too minute to be either perceptible by the human eye, of comprehensible by the human understanding.
We cannot better conclude this brief outline of the history of fossil Polyparies, extending as they do, from the most early transition rocks to.the present seas, than in the words with which Mr. Ellis expresses the feelings excited in his own mind by his elaborate and beautiful investigations of the history of living Corallines.
"And now, should it be asked, granting all this to be true, to what end has so much labour been bestowed in the demonstration? I can only answer, that as to me these disquisitions have opened new scenes of wonder and astonishment, in contemplating how variously, how extensively, life is distributed through the universe of things, so it is possible, that the facts here related, and these instances of nature animated in a part hitherto unsuspected, may excite the like pleasing ideas in others; and, in minds more capacious and penetrating, lead to farther discoveries, farther proofs, (should such yet be wanting,) that One infinitely wise, good, all-powerful Being has made, and still upholds, the Whole of what is good and perfect; and hence we may learn, that, if creatures of so low an order in the great scale of Nature, are endued with faculties that enable them to fill up their sphere of action with such Propriety, we likewise, who are advanced so many gradations above them, owe to ourselves, and to Him who made us and all things, a constant application to acquire that degree of Rectitude and Perfection, to which we also are endued with faculties of attaining."—Ellis on Corallines, p. 103.
- I found many years ago fossil Echinidans in the Carboniferous limestone of Ireland, near Donegal, they are however rare in the Transition formation, become more frequent in the Muschelkalk and Lias, and abound throughout the Oolitic and Cretaceous formations.
- These animals form the subject of an elaborate and excellent work, by Mr. Miller, entitled a Natural History of the Crinoidea, or Lily-shaped Animals. The representations at Pl. 48, and Pl. 49, Fig. 1. of one of the most characteristic species of this family, being that to which the name of stone-lily was first applied; and the figures of two other species at Pl. 47, Fig. 1, 2, 5, will exemplify the following definition given of them by Mr. Mi1ler, "An animal with a round, oval, or angular column, composed of numerous articulating joints, supporting at its summit, a series of plates, or joints, which form a cup-like body, containing the viscera, from whose upper rim proceed five articulated arms, dividing into tentaculated fingers, more or less numerous, surrounding the aperture of the mouth, (Pl. 47. Figs. 6, x. 7, x) situated in the centre of a plated integument, which extends over the abdominal cavity, and is capable of being contracted into a conical of proboscal shape."
- The comatula. presents a conformity of structure with that of the Pentacrinite, almost perfect in every essential part, excepting that the column is either wanting, or at least reduced to a single plate. Peron states that the Comatula suspends itself by its side arms from fuci, and Polyparies, and in this position watches for its prey, and attains it by its spreading arms and fingers. Miller, p. 182.
- The monograph of Mr. Miller, exhibiting the minute details of every variation in the structure of each component part in the several Genera of the family of Crinoïdea, affords an admirable exemplification of the regularity, with which the same fundamental type is rigidly maintained through all the varied modifications that constitute its numerous extinct genera and species.
- These so-called Ossicula are not true bones, but partake of the nature of the shelly Plates of Echini, and the calcareous joints of Star-fishes.
- As the contractile fibres of radiated animals are not set together in the same complex manner as the true muscles of the higher orders of animals, the term Muscle, in its strict acceptation, cannot with accuracy be applied to Crinoïdeans; but, as most writers have designated by this term the more simple contractile fibres which move their little bones, it will be convenient to retain it in our descriptions of these animals.
- Organic Remains, vol. ii. P. 180.
- Although the names here used are borrowed from the skeleton of vertebrated animals, and are not strictly applicable to radiated Echinoderms, it will be convenient to retain them until the comparative anatomy of this order of animals has been arranged in some other more appropriate manner.
Bones of the Pelvis 5 Ribs 5 Clavicles 5 Scapulæ 5 Arms, Six bones in each of the ten arms 60Hands. Each hand being formed of two fingers, and each finger consisting of at least 40 ossicula, these in 20 fingers make 800Tentacula. 30 proceeding from each of the 6 bones in each of the ten arms, make 180030 proceeding, on the average, from each of the 800 bones of the fingers make 24,0OO ———— Total 26,680
- The body (Pl. 49, Pig. 1) is supported by a long vertebral column attached to the ground by an enlargement of its base (Pl. 49, Fig 2.) It is composed of many cylindrical thick joints, articulating firmly with each other, and having a central aperture, like the spinal canal in the vertebra of a quadruped, through which a small alimentary cavity descends from the stomach to the base of the column, Pl. 49, Fig. 4, 6, 8, 10. The form of the column nearest the base is the strongest possible, viz. cylindrical. This column is interrupted, at intervals, which become more frequent as it advances upwards, by joints of wider diameter and of a globular depressed form (Pl. 49, Fig. 1, and Figs. 3, 4, a, a, a, a.) Near the summit of the column, (Pl. 49, Figs. 3, 4,) a series of thin joints, c, c, c, is placed next above and below each largest joint, and between these two thin joints, there is introduced a third series, b, b, b, of an intermediate size. The use of these variations in the size of the interpolated joints was to give increased flexibility to that part of the column, which being nearest to its summit required the greatest power of flexion.
At Plate 49, Figs. 6, 8, 10, are vertical sections of the columnar joints 5, 7, 9, taken near the base; and show the internal cavity of the column, to be arranged in a series of double hollow cones, like the inter vertebral cavities in the back of a fish, and to be, like them, subsidiary to the flexion of the column; they probably also formed a reservoir for containing the nutritious fluids of the animals.The various kinds of Screw stone so frequent in the chert of Derbyshire, and generally in the Transition Limestone, are casts of the internal cavities of the columns of other species of Encrinites, in which the cones are usually more compressed than in the column of the E. moniliformis.
- At Pl. 49, Fig. 4 is a vertical section of Fig. 3, being a portion taken from near the summit of the column, where the greatest strength and flexure were required, and where also the risk and injury and dislocation was the greatest; the arrangement of these vertebræ is therefore more complex than it is towards the base, and is disposed in the following manner (see Fig. 4.) The vertebræ, a. b. c. are alternately wider and narrower; the edges of the latter, c. are received. into, and included within, the perpendicularly lengthened margin of the wider, a. b.; the outer crenelated edge of the narrower included vertebræ, articulate with the inner crenelated edge of the wider vertebræ, which thus surround them with a collar, that admits of more oblique flexion than the plane crenelated surfaces near the base of the column, Figs. 9, 10, and at the same time renders dislocation almost impossible.
To these is superadded a third contrivance, which still further increases the flexibility and strength of this portion of the column, viz. that of making the alternate larger joints, b. b. considerably thinner than the largest collar joints, a. a.
The figures numbered from 11 to 26 inclusive, represent single vertebræ taken from various portions of the column of Encrinites moniliformis. The joints at Figs. 11, 13, 15, 17, 19, 21, 23, 25, are of their natural size and in their natural horizontal position, and show, at the margin of each, a crenated edge, every tooth of which articulaled with a corresponding depression near the margin of the adjacent joint. The stellated figures (12, 14, 16, 18, 20, 22, 24, 26,) placed beneath the horizontal joints to which they respectively belong, are magnified representations of the various internal patterns presented by their articulating surfaces, variously covered with an alternate series of ridges and grooves, that like the cogs of two wheels, articulate with corresponding depressions and elevations on the surfaces of the adjacent vertebræ.
- "On the summit of the vertebral column are placed successive series of little bones, see Pl. 50, Fig. 4, which from their position and uses may be termed the Pelvis E, Scapula H, Costal F, forming (with the pectoral and capital plates) a kind of sub-globular body (see Pl. 48. Pl. 49. Fig. 1. Pl. 50, Figs. 1, 2,) having the mouth in its centre and containing the viscera and stomach of the animal, from which the nourishing fluids were admitted to an alimentary cavity within the column, and also carried to the arms and tentaculated fingers." From the Scapula (H) proceeded the five arms, (Pl. 50, Fig. 1, K) which, as they advanced, subdivided into hands (M) and fingers (N) terminating in minute tentacula (Pl. 50. Figs. 2, 3,) the number of which extended to many thousands. These hands and lingers are represented as closed, or nearlyclosed, in Pl. 48. and Pl. 49, Fig. 1. and Pl. 50, Figs. 1, 2. In Mr. Miller's restoration of the Pear Encrinite (Pl. 47, Fig.1) they are represented as expanded. in search of food. These tentaculated fingers, when thus expanded, would form a delicate net, admirably adapted to detain Acalephans, and other minute molluscous animals that might be floating in the sea, and which probably formed part of the food of the Crinoïdea. In the centre of these arms was placed the mouth (Pl. 47, Fig. 1,) capable of elongation into a proboscis. Pl. 47. 6, x. 7, x. represent the bodies of Crinoïdea from which the arms have been removed.
In Pl. 50, Fig. 1 represents the superior portion of the animal, with its twenty fingers closed like the petals of a closed lily. Fig. 2 represents the same partially uncovered, with the tentacula still folded up. Fig. 3 is a side view of one of the fingers with its tentacula. Fig. 4 represents the interior of the body which, contained the viscera. Fig. 5 represents the exterior of the same body, and the surface by which the base articulates with the first joint of the vertebral column. Figs. 6, 7, 8, 9, represent a dissection of the four series of plates that compose the body, forming successively the scapulæ, upper and lower costa] plates, and pelvis of the animal. Fig. 10 is the upper extremity of the vertebral column. Fig 11 represents the upper surfaces of the five scapula, showing their articulations with the inferior surfaces of the first bones of the arms. Fig. 12 is the inferior surface of the same series of scapular plates, showing their articulations with the superior surfaces of the upper, or second series of costal plates, Fig. 13. Fig. 14 is the inferior surface of Fig. 13, and articulates with the first or lower series of costa] plates, Fig 15. Fig. 16 is the lower surface of Fig. 15, and articulates with the upper surface of the bones of the pelvis, Fig. 17. Fig. 18 is the inferior surface of the pelvis, Fig. 17, and articulates with the first or uppermost joint of the vertebral column, Fig. 10.
- Our Pl. 47 gives Mr. Miller's restoration of two other genera; fig 1, the Apiocrinites rotundus, or Pear Encrinite, with its root or base of attachment, and its arms expanded. Fig. 2 is the same with its arms contracted. Two young individuals and the broken stumps of two other small specimens, are seen fixed by their base to the root of the larger specimens, showing the manner in which these roots are found attached to the upper surface of the great oolite at Bradford near Bath. When living, their roots were confluent, and formed a thin pavement at this place over the bottom of the sea, from which their stems and branches rose into a thick submarine forest, composed of these beautiful Zoophytes. The stems and bodies are occasionally. found united, as in their living state; the arms and fingers have almost always been separated, but their dislocated fragments still remain, covering the pavement of roots that overspreads the surface of the subjacent Oolitic limestone rock. This bed of beautiful remains has been buried by a thick stratum of clay. Fig. 3 represents the exterior of the body, and the upper columnar joints of this animal, about two-thirds of the natural size. Fig. 4. is 9. longitudinal section of the same, showing the cavity for the viscera, and also the large open spaces for the reception of nourishment between the uppermost enlarged joints of the column.
At fig. 5 we have the Actinocrinites 30~dactylus, from the carboniferous limestone near Bristol. D. represents the auxiliary side arms which are attached to the column of this species, and B its base and fibres of attachment. Fig. 6 represents its body, from which the fingers are removed, showing the pectoral plates, Q, and capital plates, R, which form an integument over the abdominal cavity of the body, and terminate in a mouth (X,) capable of being protruded into an elongated proboscis by the contraction of its plated integument. Fig. 7 represents the body of an Encrinite in the British Museum, figured by Parkinson, vol. 2, fol. 17, fig. 3, by the name of Nave Encrinite. The mouth of this specimen also is seen at X, and between the mouth and the bases of the arms, the series of plates which form the upper and exterior integuments of the stomach.
- Fragments of Encrinites are also dispersed irregularly throughout all the depositions of this period, intermixed with the remains of other contemporary marine animals.
- See Miller's Crinoïdea, p. 45.
- See Memoir on Pentacrinus Europzus by T. V. Thompson, Esq. Cork, 1827. He has subsequently ascertained that this animal is the young of the Comatula.
- See the tubercles and corrugations on the surfaces of the bones engraved at Pl. 52, Figs. 7, 9,11, 13, 14, 15, 16, 17.
- Pl. 51 represents s single specimen of Briarean Pentacrinite, which stands in high relief upon the surface of a slab of Lias, from Lyme Regis, almost entirely made up of a mass of other individuals of the same species. The arms and lingers are considerably expanded towards the position they would assume in searching for food. The side-arms remain attached to the upper portion only of the vertebral column.
At Pl. 53. Fig. 1 and 2 represent two other specimens of the same species, rising in beautiful relief from a slab, which is composed of a congeries of fragments of similar individuals. The columns of these specimens, Fig. 2, a, show the side-arms rising in their natural position from the grooves between the angular projections of the Pentagonal stem. At Pl. 52, Fig. F (a). F (b). are seen the costal plates surrounding the cavity of the body; at H, the Scapulæ, with the arms and lingers proceeding from them to the extremities of the tentacula.
At Pl. 53. Fig. 3. exhibits the side-arms rising from the lower part of a vertebral column, and entirely covering it. Fig. 4. is another column, on which, the side-arms being removed, we see the grooves wherein they articulated with the alternate vertebræ. Fig. 5. exhibits a portion of another column slightly contorted.
- The columnar joints of the Briarean Pentacrinite are disposed in pieces alternately thicker and thinner, with a third and still thinner joint interposed between every one of them. Pl. 53. Figs. 8, and 8a, a. b. c. The edges of this thinnest joint appear externally only at the angles of the column; internally they enlarge themselves into a kind of inter vertebral collar, c. c. c.
A similar alternation in joints of the Pentacrinites sub-angular is is represented in Pl. 52. Figs. 4 and 5.
- The ranges of tubercles upon the exterior surface of each joint in the fragments of columns, Pl. 52. Figs. 7. 9. 11. mark the origin and insertion of muscular fibres, by which the.movement of every joint was regulated. At every articulation of the vertebrae, we see also the mode in which the crenated edges lock into one another, combining strength with flexibility. In Pl. 52, Figs. ll. and 13, the Vertebræ (d.) present five lateral surfaces of articulation, whereby the side-arms were attached to the vertebral column at distant intervals, as in the Pentacrinus Caput Medusæ, Pl. 52. Fig, 1.
The double series of crenated surfaces, which pass from the centre to the points of each of the five radii of these star-shaped vertebra, Pl. 52. Fig. 6. to 17.; and Pl. 53. Figs. 9. to 13, present a beautiful variety of arrangements, not only in each species, but in different parts of the column of the same species, according to the degree of flexion which each individual part required.
- Mr. Miller describes a recent specimen of Pentacrinus Caput Medusæ, as having the joints next to the base partially consolidated, and admitting but little motion, where little is required; but higher up, the joints become thinner, and are disposed alternately, a smaller and thinner joint succeeding a larger and thicker, to allow a greater freedom of motion, till near the apex this change is so conspicuous, that the small ones resemble thin leather-like inter positions. He also observed traces of the action of contractile muscular fibres on the internal surfaces of each vertebra.
- The specimens of Briarean Pentacrinite at Pl. 52, Fig. 3. from the Lias at Lyme Regis, adheres laterally to a portion of imperfect jet, which forms part of a thin bed of Lignite, in the Lias marl, between Lyme and Charmouth.
Throughout nearly its whole extent, Miss Anning has constantly observed in this Lignite the following curious appearances: The lower surface only is covered by a stratum, entirely composed of Pentacrinites, and varying from one to three inches in thickness; they lie nearly in a horizontal position, with the foot stalks uppermost, next to the lignite. The greater number of these Pentacrinites are preserved in such high perfection, that they must have been buried in the clay that now invests them before decomposition of their bodies had taken place. It is not uncommon to find large slabs several feet long, whose lower surface only presents the arms and lingers of these fossil animals, expanded like plants in a Hortus Siccus; whilst the upper surface exhibits only a congeries of stems in contact with the under surface of the lignite. The greater number of these stems are usually parallel to one another, as if drifted in the same direction by the current in which they last floated.
The mode in which these animal remains are thus collected immediately beneath the Lignite, and never on its upper surface, seems to show that the creatures had attached themselves, in large groups, (like modern barnacles,) to the masses of Boating wood, which, together with them, were suddenly buried in the mud, whose accumulation gave origin to the marl, wherein this curious compound stratum of animal and vegetable remains is imbedded. Fragments of petrified wood occur also in the Lias, having large groups of Mytili, in the position that is usually assumed by recent mytili, attached to floating wood.
- If we suppose the lower portion of the specimen, Pl. 53, Fig; 2. a. to be united to the upper portion of the fractured stem, Fig. 3, we shall form a correct idea of the manner in which the column of this animal was surrounded with its thousand side-arms, each having from fifty to a hundred joints, Pl. 53, Fig. 14. The number of joint: in the side-arms gradually diminishes towards the top of the vertebral column; but as one of the lowest and largest (Pl. 53, Fig. 14.) contains more than a hundred, we shall be much below the reality in reckoning fifty as their average number.
Each of these joints articulates with the adjacent joint, by processes resembling a mortice and tenon; and the form both of the articulating surfaces and of the bone itself] varies so as to give more universal motion as they advance towards the small extremity of the arm. See Pl. 53, Fig. 14. a. b.
In all this delicate mechanism which pervades every individual side-arm, we see provision for the double purpose of attaching itself to extraneous bodies, and apprehending its prey. Five of these arms are set off from each of the largest joints of the vertebral column. At Pl. 53. Fig. 7. a. we see the bases, or first joints of these side-arms articulating with the larger vertebræ, and inclined alternately to the right and left, for the purpose of occupying their position most advantageously for motion, without interfering with each other, or with the flexure of the vertebral column.
In the recent Pentacrinus Caput Medusa (Pl. 52, Fig. 1.) the sidea-arms (D.) are dispersed at distant intervals along the column.
- 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."
- Tiedemann, in monograph on Holothuria, Echini, and Asterix, 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.
- 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 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 inter tropical 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.
- Ehrenberg has ascertained that the Infusoria, which have heretofore been considered as scarcely organized, have an internal structure resembling that of the higher animals. He has discovered in them muscles, intestines, teeth, different kinds of glands, eyes, nerves, and male and female organs of reproduction. He finds that some are born alive, others produced by eggs, and some multiplied by spontaneous divisions of their bodies into two or more distinct animals. Their powers of reproduction are so great, that from one individual (Hydatina senta) a million were produced in ten days; on the eleventh day four millions, and on the twelfth sixteen millions. The most astonishing result of his observations is, that the size of the smallest coloured spots on the body of Monas Termo, (the diameter of which is only of a line) is of a line, and that the thickness of the skin of the stomach may be calculated at from to of a line. This skin must also have vessels of a still smaller size, the dimensions of which are too minute to be ascertained. Abhandlungen der Academie der Wissenschaften zu Berlin, 1831.
Ehrenberg has described and figured more than 500 species of these Animalcules; many of them are limited to a certain number of vegetable infusions; a few are found in almost every infusion. Many vegetables produce several species, some of which are propagated more readily than others in each particular infusion. The familiar case of the rapid appearance and propagation of animalcules in pepper water will suffice to illustrate the rest.
In the London and Edin. Phil. Mag. Aug. 1, 1836, p. 158, there is an extract of a letter sent by M. Alexander Brongniart from Berlin to the Royal Academy of Sciences of Paris, announcing that Ehrenberg has also discovered the silicified remains of Infusoria in the stone called Tripoli (Polie-schiefer of Werner,) a substance which has been supposed to be formed from sediments of fine volcanic ashes in quiet waters. These petrified Infusoria from a large proportion of the substance of this kind of stone from four different localities, on which Ehrenberg has made his observations; they were probably living in the.waters, at the time when they became charged with the volcanic dust, in which the Tripoli originated. It is added in this notice that the slimy Iron ore of certain marshes is loaded with Infusoria, of the genus Gallionella.—L'Institut, No. 166.
These most curious observations throw important light on the obscure and long-disputed question of equivocal generation; the well-known fact that animalcules of definite characters appear in infusions of vegetable and animal matter, even when prepared with distilled water, receives a probable explanation, and the case of Infusoria no longer appears to differ from that of other animals as to the principle on which their propagation is conducted. The chief peculiarity seems to consist in this, that their increase takes place both by the oviparous and viviparous manner of descent from parent animals, and also by division of the bodies of individuals.
The great difficulty is, to explain the manner in which the eggs or bodies of preceding individuals can find access to each particular infusion. This explanation is facilitated by the analogous cases of various fungi which start into life, without any apparent cause, wherever decaying vegetable matter is exposed to certain conditions of temperature, humidity, and medium. Fries explains the sudden production of these plants, by supposing the light and almost invisible sporules of preceding plants, of which he has counted above 10,000,000 in a single individual, to be continually floating in the air, and falling every where. The greater part of these never germinate, from not falling on a proper matrix; those which find such matrix start rapidly into life, and begin to propagate.
A similar explanation seems applicable to the case of Infusoria; the extreme minuteness of the eggs and bodies of these animalcules probably allows them to float in the air, like the invisible sporules of fungi; they may be raised from the surface of fluids by various causes of attraction, perhaps even by evaporation. From every pond or ditch that dries up in summer, these desiccated eggs and bodies may be raised by every gust of wind, and dissipated through the atmosphere like smoke, ready to start into life whenever they fall into any medium admitting of their suscitation; Ehrenberg has found them in fog, in rain, and snow.
If the great aerial ocean which surrounds the earth be thus charged with the rudiments of life, floating continually amidst the atoms of dust we see twinkling in a sunbeam, and ever ready to return to life as soon as they find a matrix adapted to their development, we have in these conditions of the very air we breathe a system of provisions for the almost infinite dissemination of life throughout the fluids of the present Earth; and these provisions are in harmony with the crowded condition of the waters of the ancient world, which is manifested by the multitudes of fossil microscopic remains, to which we have before alluded. (See Sect. viii. page 290.)
Mr. Lonsdale has recently discovered that the Chalk at Brighton, Gravesend, and near Cambridge, is crowded with microscopic shells; thousands of these may be extracted from a small lump, by scrubbing it with a nail brush in water; among these he has recognised vast numbers of the Valves of a marine Cypris (Cytherina) and sixteen species of Foraminifers.