having been discharged from the rectum 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, passed 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 constitutes 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
cluster of shelly 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 shelly 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 fashion; 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.
[Illustration: SERPULA.]
Who could hesitate to assert 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 space, if the two edges of the
band meet; or a semi-cylindrical space, 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-shore, 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 passing
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.
The entire edifice has been built around her; she is the hope of the
colony, the only mother in this vast assemblage. It is therefore
through her that we must look for a past history; and in her we find it.
Some months ago, when she was not more than one thousandth part as large
as she is now, though then adult, she migrated from some other city not
less populous than this is now. It was just before the periodical rains,
when, at the time of the great annual swarming, myriads of winged males
and females were evolved from the pupa state, and flew out from their
native city. This individual female was found by some of the workers
that now compose this colony, and was immediately selected to be at once
their prisoner and their queen.
We thus trace our great egg-laying Termes to a city of last year's
building, in which for a time she was in an immature condition as a
nymph, and before that passed a still less-developed stage as a larva.
Hence her life-history goes yet farther back to an egg, originally laid
by a former female in exactly the same circumstances as those in which
we find this guarded and immured individual.
Thus we reason; but the female, with her host of attendants, and the
house, which is inseparable from their present stage of existence, has
been created to-day.
See that creature which with loud ringing hum is whirling round and
round the tassel-like blossoms of this noble _Eugenia_. You would think
it a bird from its massive size, but it flashes and sparkles in the sun,
like a great jewel. Now it suddenly alights on one of the crimson
flowers, and you may perceive that it is a beetle;--a beetle of vast
size, and glittering like a lump of burnished metal;--it bears the name
of Goliath,--a giant clad in polished armour.
This is his first hour of existence; now for the first time has his
nervous system responded to the stimulus of the sweet air and genial
sunshine. An hour ago he had no nervous system; no system of any sort;
no life; no being; no anything;--he was not until this hour.
Yet if we were to ask a friend conversant with entomology his opinion on
the age of this insect, he would immediately give it; not, however, as
an opinion, for he would repudiate the uncertainty which such a word
implies, but as an indubitable fact, resting on the infallible grounds
of constant observation and undeviating experience.
[Illustration: GOLIATH BEETLE, AND PUPA CASE.]
"This fine _Goliathus_," he would say, "has not long, probably, emerged
from a hollow case of oval form, made of particles of earth agglutinated
together by a secretion from the mouth of the larva, and concealed under
the surface of the ground. Within that sepulchre it has left its
cerements,--the shrivelled skin of the pupa, in which it had been
wrapped up motionless like a mummy, for several weeks prior to its
appearance as a glittering beetle. The construction of the oval cell was
the last act of the larva, a thick, massy, heavy-bodied grub, which had
fattened for years by feeding on the roots of plants beneath the soil.
Four years passed away[69] while yon beetle lay on its side, darkly
labouring at this occupation; and before that it was a minute egg for
some weeks. The specimen before us cannot be far short of five years
old."
No such thing: the witness is at fault: the _Goliathus_ is not _an hour_
old.
Take notice of the swarm of Gnats, which, like a dim cloud, are uniting
in choral dance and song in the beam of the setting sun. Every member of
the band that "winds his shrill horn," has had an aquatic before he had
an aerial existence. A week was spent, in lobster-shape, with two
breathing tubes on the summit of his body, in passing alternately from
the bottom to the top of yonder stagnant pool, and then back from the
top to the bottom. And a month was occupied in pretty nearly the same
employment, but in another mask,--in fish-like form, with the
star-tipped breathing-tube projecting from the side of the tail. But for
some months earlier still it was a little lenticular egg, which was
agglutinated with a number of others into an oval concave boat, that
floated to and fro on the surface of the pool.
And there was something worth observing in that tiny skiff of eggs; for
it did, in its artful construction, carry the evidence of time back to a
former generation. The eggs individually and separately would have sunk
to the bottom of the water; it was, however, essential to their life
that they should be in contact with the air as well as with the water.
Hence they were so arranged in the aggregate, that the mass should swim,
though the constituent individuals could not. To effect this, the parent
Gnat, resting on the calm surface of the pool, crossed her two hind
legs, and laid an egg perpendicularly in the angle so made: others were
added in succession, all maintaining the perpendicular position, all
glued together by a cement that resists water, but so arranged, the
crossed legs being still the mould, that the outline should be
spindle-shaped, while the summits of the central eggs, being a little
lower than those of the outer ones, gave a concavity to the boat. So
buoyant was it when finished, and the mother's legs withdrawn, that even
a drop of water falling full upon it from above, would have failed to
submerge it. There it floated, week after week, and month after month,
all through the winter, till the genial sun of spring hatched the
fish-like larvae to begin their wriggling existence beneath the surface.
Now may we not say with confidence, that the sounding-winged insect
looks back to the pupa, the pupa to the larva, the larva to the
egg-boat? And more, that the form of the boat,--a form so essential that
it could not have lived without it,--looked back to the crossed feet of
the mother-gnat, the impress of whose angle its extremities sustained?
Of course we might reason thus: but yet we should be at fault; for the
ringing swarm of merry Gnats has been this very evening created.
[Illustration: LARVA OF CASE-FLY.]
The Case-flies (_Phryganea_) that look like delicate moths of
sober-brown hue, flitting over the surface of the pond, have, like the
Gnats, spent a considerable time under water. When they were larvae, they
industriously collected small shells, fragments of stone, bits of reed,
and the like matters, and, connecting them together with strong silk,
made out of them slender tubes, in which they sheltered their soft
bodies from harm, while their hard polished heads and shoulders
projected from the open end. And after having lived through the winter
(at least, but I rather think more than _one_ winter) in this state,
each closed up the entrance of his castle, by spinning across its open
end, a transverse screen of lattice-work, made of very strong and stout
silk, which, while it should serve the purpose of keeping out
evil-minded intruders, during the helpless inaction of the pupa, should
at the same time admit the free ingress and egress of water necessary
for its respiration.
The life of the larva, and the exercise of these, its curious instincts,
are, together with the duration of the pupa stage, inseparable
precedents of the imago state in which we now observe the flying
insects. No, not "inseparable;" for in this case, at least, they had no
existence in time; they are prochronic developments.
[Illustration: MELICERTA.]
In this pond at our feet there is an object worthy of a moment's
observation, minute though it is, for it is only visible as a speck to
the unassisted eye. On one of the whorl-filaments of this tuft of
_Myriophyllum_, there stands up a cylindrical tube, firmly adherent to
the plant by its foot, but free at its upper end. Small as it is, this
chimney is built up of hundreds of pellets, solid, round, and yellow;
placed in symmetrical order, and firmly cemented together. What has
made this tube? Ha! here is the little architect ready to answer for
himself; he thrusts out his head and shoulders from his chimney-top, and
announces his scientific cognomen as _Melicerta ringens_.
Look! he is in the very act of building now. Did you see him suddenly
bow down his head and lay a brick on the top of the last course? And now
he is busy making another brick; his mould is a tiny cup-shaped cavity
just below his chin; his material the floating floccose atoms of
vegetable refuse. Cilia along his flower-like face collect these atoms
into a stream, and pour them into the cup; and cilia within the cup
whirl them rapidly round and round in many rotations, until with the aid
of mucus they are somewhat consolidated into a round pellet. The brick
is made, and nothing remains but that it be deposited next the former,
in regular progression, and this is done by the tiny [Greek: tekton],
suddenly bending his head forward, and bringing the chin-cup with exact
precision to the spot.
And how long has he been engaged in this piece of work? Little more than
a day. It was commenced yesterday, when the creature was not more than
one-third as large as he is now. But he had lived a few hours before the
commencement of his work. He was a rover before he began to be a
house-keeper. In that early stage of youth and freedom, before he had
made up his mind to settle in life, he had no chin-cup, no flower-like
face, and of course no tube. A cylindrical gelatinous pellucid worm, he
issued out of the egg, with a brush of cilia on his crown, and danced
waywardly through the water. While thus occupied, his form underwent
some preliminary modifications, and at length was sufficiently matured,
to enable him to choose a spot for the passing of his future life, and
to commence the building on which he is still engaged.
Not so. The pellet which he deposited when we began to look at him, was
the first he had ever made; he had been created but that moment; and all
the previous pellets of the case had been called into being just as we
saw them. They were built up prochronically.
I tear a piece of bark from the trunk of this half-decayed tree, and
have disclosed amidst the rank-smelling damp and rotten wood, a large
_Julus_, a slow-moving creature, with some hundred-and-fifty little
twinkling feet. As this specimen has attained its adult condition, it
must be at least two years old; for it does not acquire its
reproductive organs and perfect development till that age.[70]
This creature has passed through a rather curious history of evolutions.
The egg from which it was produced was lodged in a chamber excavated by
the parent, a few inches below the surface of the rotten mould. From
this egg proceeded a little kidney-shaped body, without limbs or motion,
completely enveloped in a swathe of delicate transparent membrane. About
a fortnight it remained in this helpless state, during which its organs
had been forming out of the constituent cells, by repeated subdivision,
and definite arrangement. At length it burst its cerement, and a minute
Julus appeared, not more than 1/200th of an inch in length, composed
of a head with antennae, and a body of eight segments, of which the first
three carried each a pair of legs.
All the multitudinous limbs which we see in this adult have been
produced in successive moultings, and all the numerous segments have
been produced by the subdivision of the last but one,--that is the joint
preceding the anal one,--six at a time.
By the time the little animal was ready for the second sloughing, that
is, in about a week after the preceding, three more pairs of feet were
seen, which had budded from the fourth, fifth, and sixth segments, but
which were as yet closely packed down beneath the investing skin; the
seventh segment also was obscurely marked into six divisions. The skin
was now thrown off, and these changes were perfected; the little Julus
now had six pairs of feet, and thirteen segments.
This process was repeated again and again; the new limbs always
developing on the segments last produced, and six new segments being
always formed out of the existing penultimate. And by this gradual
succession of development, the animal has attained the number of limbs
and segments which we now perceive. The antennae and the eyes have
likewise passed through successive stages.
We have a right to infer the lapse of a period sufficient to produce
these changes, for we see their indubitable results; but our inference
would only lead us astray, because we have not allowed for a disturbing
influence,--that of the Law of Creation. This is the Julus's first hour
of life.
See, on the trunk of that towering _Cedrela_, a round hole, out of which
a large Beetle is in the act of emerging. It is a noble _Buprestis_,
encased in glittering mail, of the most refulgent metallic splendour,
crimson, gold, and green. Can we find any clue to his age? Yes: the
white grab has rioted and fattened in its burrows in the timber of this
tree for many years; ever gnawing away with its horny auger-like jaws
the solid wood in tortuous galleries, which constantly enlarged, as it
progressively grew, while its wake, as it advanced, was partially filled
by its ordure. The old tree is, no doubt, perforated, through and
through, by its winding corridors, as large as your middle finger. As
soon as the vermin had passed this his nonage, which, as I say, may have
occupied a dozen years at least,[71] he sank into his short pupa-sleep,
and here we see him paying his first visit to the light of day.
True; this is his first experience of daylight, and indeed of anything;
for all the pupa-sleep and the larva-labour were prochronic in this
case. The Beetle is just created.
Hark to that hollow roar! There is no mistaking that majestic sound. It
is the voice of the many-sounding sea. Yonder through the trees we catch
a glimpse of its shining face, and here we are at the verge of the
cliffs, against whose feet the waves are breaking in white foam. We
will clamber down to the rocks.
In this weed-fringed tide-pool there is a fine specimen of the
Shore-crab (_Carcinus moenas_). It is a male just arrived at the
perfection of adult age; its carapace smooth and wholly dark-green in
hue, its under parts rufous orange. Its claws. are large and sharp; and
the promptitude with which it presents these formidable weapons,
extended to the utmost, shows how conscious it is of its warlike powers.
To all appearance this Crab is several years old;[72] I mean in this his
present perfect or imago form. When this form was first assumed, the
diameter of the carapace was not more than an eighth of an inch; it is
now two inches; a great many periodical sloughings of the crust must
have occurred to accomplish this sixteen-fold increase.
But four distinct metamorphoses were passed before the commencement of
this form. There was the Grapsoid form with the outline of the carapace
nearly parallel-sided, and the dentations on the sides. Before this
there was the Megalopa form, with the carapace ovate, and the abdomen
projecting behind. Before this there was the Zoea form, with the
carapace rising into a tall erect spine, sessile eyes, no claws, and the
abdomen a slender jointed cord ending in a triangular plate. And before
this, there was the egg, which was laid by the mother Crab, and carried
by her for a considerable time attached to the false feet of her
abdomen.
All these evidences of age, clear and unanswerable though they are, are
yet fallacious, because the Crab has been created but this morning.
On this sea-washed branch of a tree, which has been blown off by some
tempest, and carried into the ocean, there is a single Barnacle
(_Lepas_). It consists of a hand of many pairs of fringed fingers,
protected by a shell of five pieces, and a long flexible cartilaginous
stalk, by the lower extremity of which it adheres to the timber.
The shelly valves are all crossed by strongly marked lines running over
their surfaces in a direction parallel with each other, and with the
outer margins of each valve. These, like the corresponding foliations in
the tube of the _Serpula_, indicate the successive stages of growth; the
outlines of every valve having stood at each of these growth lines in
succession. On each of the scutal valves in this individual I can count
about 260 growth-lines: if we suppose one of these to be made in a
week,[73] and the increase to proceed uniformly throughout the year, we
must conclude the valve to have been just five years in making.
[Illustration: LEPAS.]