Part 10 (1/2)

Clearly, therefore, we have a right to infer a past history of the Urchin, and that of not a few distinct stages. But no; the specimen has commenced its history within an hour!

Yonder Feather-star (_Comatula_) notice; which, having just now started into mature life at the almighty fiat of its Creator, goes careering joyously through the sea, expanding and contracting its many-jointed and feathery arms, as if it had been accustomed to the alternation for a long life, and ever and anon settling itself by grasping the points of rock with its dorsal claws. You would hardly think that those flexible and slender arms were made of stone: yet they are; every joint of the stems and of their pinnae is a vertebra of stone (precious stones, you will say--topaz and ruby--from their brilliant hues), which has been formed and deposited atom by atom, by the slow and gradual process of secretion of calcareous matter; the lime having been primarily collected from the sea-water which held it in solution. At least, such is the physiological deduction.

[Ill.u.s.tration: COMATULA AND YOUNG.]

But there was a period in the _Comatula's_ history when it was not a free-swimming star, but a lily-like flower of ten slender fringed petals, seated at the summit of a long stalk, with a central columnar axis of stone. Before that, the flower-head had a bud-like figure, and the petals were minute and dest.i.tute of lateral fringes; and earlier still, it was a tiny gelatinous club without any development of stone, affixed by a spreading base, and shooting forth from the top a few pellucid processes. Earlier still, it was, no doubt, an infusory-like gemmule, clothed with cilia.

Through all these successive stages, which, of course, occupied a considerable period of time, we should certainly affirm the Feather-star to have pa.s.sed, did we not know that it has this very hour burst into existence.

That Panther, whose tawny fur studded with black rosettes appeared so beautiful as he bounded with agile grace from glade to glade just as we emerged from the forest, contains within his intestines, though you cannot see it, a mature Tapeworm. The body of this parasite consists of some hundreds of square flattened segments, each of which includes a complicated generative apparatus, equal to the production of thousands of fertile ova. Is not this an evidence of age? For, first of all, consider that the formation of each of these hundreds of joints has been a work of development from the anterior parts; and therefore they record as many distinct and successive processes as there are segments. And, secondly, remember that the _Taenia_ did not commence existence as a _Taenia_, nor in the conditions in which it now exists, within the bowels of the Panther. It looks back to another form, and to another living _nidus_.

There was a time when this parasitic creature had no ribbon-like body of flattened generative segments. There was, indeed, the same curious head, a tiny globose k.n.o.b at the extremity of a slender neck, furnished with the same array as now, of rows of hooks and sucking disks. But in place of the segments, the neck merged into a membranous bladder distended with clear fluid. It was not a _Taenia_ then, but a _Cysticercus_.

Its home was at that time the interior of a living animal on whose vitalized juices it was sustained, but that animal was widely different from its present patron. It was an Antelope, that cropped the wiry gra.s.s and aromatic shrubs of the arid plain.

Earlier still, the germ of this _Taenia_ was an egg lying on the ground, having been discharged from the r.e.c.t.u.m of another Panther, in the bowels of which it had been developed by one of the segments of a former _Taenia_.

Let us now trace the history of this organism onwards from the point at which we have arrived in our retrograde researches.

The parent _Taenia_, still snugly ensconced in its obscene abode, partially matured and then separated the ultimate generative segment, containing many thousands of ova, far advanced towards perfection. The detached segment now became enclosed in the faeces of the Carnivore, and was at length discharged, enveloped in the pellet. The eggs, acquiring maturity, were hatched, and the infant worms individually scattered themselves among the surrounding herbage.[66]

One of these was devoured with the herbage by a grazing Antelope, and having safely escaped the perilous ordeals of mastication and rumination, pa.s.sed into the stomach of that Ruminant, whence it soon made its way by some unknown but unerring route to the liver, in the parenchyma of which organ it rapidly developed the cyst, which gave to the present stage its proper character.

The Antelope fell a prey to the ferocious Cat; its flesh was quickly digested in the stomach, but the gastric juice produced no effect on the _Cysticercus_. This parasite had merely changed its residence for one more commodious, or at least more suitable for its further development. It presently attached itself to the walls of the intestine by means of its oral hooks and suckers, and, getting rid of its vesicular sac, with its fluid contents, probably by absorption, it began to develop, joint by joint, that immense ribbon, which it possesses now, and which const.i.tutes it a Tapeworm.

Such is the ”strange eventful history” of this repulsive creature; a history legitimately deducible, in all its stages, from its presently-existing condition. But it is a history altogether illusory.

The _Taenia_ never was a _Cysticercus_: the Panther is as yet guiltless of capricide: it is this moment called into being, and the Tapeworm begins existence within it.

This lump of red sandstone that has been rolled about in the sea, till all its points and angles are worn smooth, is now roughened again by the close and firm adhesion of extraneous substance, in the form of a cl.u.s.ter of sh.e.l.ly pipes, which twine irregularly over the surface of the boulder, and then start up erect with open mouths. These are the tubes of a species of _Serpula_, and the worm itself is seen now slowly emerging from one of them, and introducing its conical stopper, and elegant fans of white and scarlet filaments, to the genial daylight.

Observe, however, that the tubes are not of the same diameter throughout. At the point where they start up from contact with the stone, they are considerably smaller than at the tip; and if we trace back the adherent portion along its tortuous course, we find that it constantly diminishes until it is but a slender white thread of stone.

Now this slender extremity was formed first; and as the worm itself grew, so it progressively required a larger and yet a larger habitation; which was readily provided of the due dimensions, because the material, which is limestone, was secreted by the swollen collar of the worm, and being freely poured out as required, was moulded of the proper calibre by the rotatory motion of the animal, combined with the special use of certain tactile organs for the purpose.

The sh.e.l.ly tubes themselves afford us ocular evidence not only of their progressive formation, but also of the successive steps by which this was effected. For at certain intervals of their length we perceive rings of the common stony substance, which mark the rim or mouth of the tube as it existed after each periodic increase. The mouth of the tube is, as we see, slightly expanded in a trumpet fas.h.i.+on; but as the general cylindrical figure is to be maintained, the next deposit of calcareous matter is not made at the very edge of the lip, but on a ring a little way within the margin, whence it is carried up, leaving the former margin slightly projecting.

[Ill.u.s.tration: SERPULA.]

Who could hesitate to a.s.sert that a history of past time is legibly written in the annulations of these stony tubes? And yet the creatures, with their tubes, have been but this instant created.

But here is a tube of quite another construction, though inhabited by a kindred worm. It is wholly built up of sand, the inimitable architecture of the indwelling _Terebella_, who has thus succeeded in performing a task which defied the efforts of that too industrious artizan,--the familiar of the renowned Michael Scott.[67] Our worm has certainly spun a rope of sand, and one which holds together with surprising tenacity.

The instrument which our little architect wrought with are the long tentacles, which, like a tangled tuft of yellow sewing-cotton, twist and twine over the floors of sandy pools. Nothing at first sight seems less adequate for the purpose than those very slender, soft, and flexible threads. Dr. Williams shall tell us how they are used. ”They consist of hollow flattened tubular filaments, furnished with strong muscular parietes. The band may be rolled longitudinally into a cylindrical form, so as to inclose a hollow cylindrical s.p.a.ce, if the two edges of the band meet; or a semi-cylindrical s.p.a.ce, if they only imperfectly meet.

This inimitable mechanism enables each filament to take up and firmly grasp, _at any point of its length_, a molecule of sand; or, if placed in a linear series, _a row_ of molecules. But so perfect is the disposition of the muscular fibres at the extreme free end of each filament, that it is gifted with the two-fold power of acting on the sucking and on the muscular principle. When the tentacle is about to seize an object, the extremity is drawn in, in consequence of the sudden reflux of fluid in the hollow interior; by this movement a cup-shaped cavity is formed, in which the object is securely held by atmospheric pressure; this power is, however, immediately aided by the contraction of the circular muscular fibres. Such, then, are the marvellous instruments by which these peaceful worms construct their habitations.”[68]

Since the slender tentacles are the implements by which the sand-tube is thus built up, it is manifest that the existence of the tube must be subsequent to the existence of the tentacles. But the _Terebella_ was at one time without tentacles; so that its history certainly reaches back to a date anterior to the existence of a tube. Several stages of life have intervened between that distinguished by the present worm-form, and its infant condition, when it swam as a ciliated undivided monad.

So, at least, we conclude from physiological data; but our conclusions are false, because contradicted by the fact that the mature animal with its case has been just now created.

Let us forsake the ocean-sh.o.r.e, and walk again through the glades of the virgin forest. A White-ant (_Termes_) crosses our path, and, by tracking him home, we speedily discover his dwelling, an enormous structure composed of gnawed wood cemented with an animal secretion, and formed into thin but very firm and hard layers. Swarms of labourers are pa.s.sing in and out; and, on our breaking away a portion of the edifice, out come crowding the warriors, with formidable jaws extended widely, ready for the fight. In the interior we find numerous chambers stored with food, and nurseries occupied by young and eggs, the number of which is every hour increasing by the oviposition of the gravid female,--the queen of the city--who is lodged in an apartment in the very centre of the whole.