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D. S. (David Samuel) Margoliouth.

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as an example, the history of Sacculina (Fig. 11, a), which exists as a
bag-like growth attached to the bodies of hermit-crabs, and sends
root-like processes into the liver of its host. Xo sign of life exists in a




Fig. 11.— Saccclina and Yocng.



sacculina beyond mere pulsation of the sac-like body, into and from
which water flows by an aperture. Lay open this sac, and we shall
find the animal to be a bag of eggs and nothing more. But trace the
development of a single egg, and one may derive therefrom lessons
concerning living beings at large, and open out issues which spread
and extend far afield from sacculina and its kin. Each egg of the
sac-like organism develops into a little active creature, possessing three
pairs of legs, generally a single eye, but exhibiting no mouth or
digestive system — parasitism having affected the larva as well as the
adult. Sooner or later, this larva— known as the nmipUus (b) — will
develop a kind of bivalve shell ; the two hinder pairs of limbs are cast
off and replaced by six pairs of short swimming-feet ; while the front
pair of limbs develops to form two elongated organs whereby the
young sacculina will shortly attach itself to a crab " host." When
the latter event happens, the six pairs of swimming-feet are cast off,
ilie body assumes its sac-like appearance, and the sacculina sinks into
its adult stage — a pure example of degradation by habit, use, and
wont. So also with certain near neighbors of these crab-parasites,
such as the Lerneans, which adhere to the gills of fishes. Beginning
life as a three-legged "nauplius," the lernean retrogresses and de-



228



THE POPULAR SCIENCE MONTHLY.



generates to become a mere elongated worm, devoted to the produc-
tion of eggs, and exhibiting but little advance on the sacculina.
There are dozens of low crustaceans which, like sacculina, afford ex-
amples of animals which are free and locomotive in the days of their
youth, but which, losing eyes, legs, digestive system, and all the
ordinary belongings of animal life, "go to the bad," as a natural result
of participating in what has been well named " the vicious cycle of
parasitism."

Plainly marked as are the foregoing cases, there are yet other
familiar crustaceans which, although not parasites, as a rule, neverthe-
less illustrate animal retrogression in an excellent manner. Such are
the sea-acorns (jBalani), which stud the rocks by thousands at low-
water mark, and such are the barna-
cles (Fig. 12), that adhere to floating
timber and the sides of ships. In the
development of sea-acorns and bar-
nacles, the first stage is essentially
like that of the sacculina. The young
barnacle is a " nauplius," three-legged,
free-swimming, single-eyed, and pos-
sessing a mouth and digestive appa-
ratus. In the next stage we again
meet with the six pairs of swimming-
feet seen in sacculina, with the enor-
mously developed front pair of legs
serving as "feelers," and with two
-^ " magnificent compound eyes," as Dar-
win describes the organs of vision.
The mouth in this second stage, how-
ever, is closed, and feeding is there-
fore impossible. As Darwin remarks,
the function of the young barnacles
"at this stage is to search out by
their well-developed organs of sense and to reach by their active
powers of swimming a proper place on which to become attached,
and to undergo their final metamorphosis. When this is com-
pleted," adds Darwin, " they are fixed for life ; their legs are now
converted into prehensile organs ; they again obtain a well-constructed
mouth, but they have no antennae, and their two eyes are now
reconverted into a minute, single, simple eye-spot." A barnacle is
thus simply a highly modified crab-like animal which fixes itself by its
head to the floating log, and which " kicks its food into its mouth
with its feet," to use the simile and description of biological authority.
The development of its " shell " and stalk are matters which do not in
the least concern its place in the animal series. These latter are local
and personal features of the barnacle tribe. For in the " sea-acorns,"




Fig. 12.— Barnacles.



THE PRIMEVAL AMERICAN CONTIXEXT. 229

which pass through an essentially similar development, there is no
stalk ; and the animal, after its free-swimming stage, simply glues its
head, by a kind of marine cement of its own manufacture, to the rock,
develops its conical shell, and like the barnacle uses its modified feet
as means for exercising the commissariat and nutritive function. It is
true that in some respects the adult barnacle may be regarded as lower
than the young, and therefore as a degenerate being. Thus, it is
lower when eyes, feelers, and movements are taken into account. In
other respects the adult may be considered of higher organization than
the larva. These higher traits we may logically enough suppose rep-
resent the special advances which adult barnacle-life has made on its
own account. But, on the whole, degradation and retrogression, if not so
fully exemplified as in the sacculina, is still plainly enough illustrated
in barnacle history. When we further reflect that even such high
crustaceans as prawns and allied forms begin life each as a "nauplius"
or under an allied guise, we not only merely discover the common
origin of all crustaceans in some form represented by the "nauplius"
of to-day, but we also witness the possibilities of development which
have placed shrimps, prawns, etc., in the foremost rank of the class, and
which, conversely, have left the barnacles and sacculinas, through the
action of degenerative changes, among the groundlings of the group.

The assumption of a sedentary life, whether parasitic in nature
like that of sacculina, or whether it is represented by mere attachment
and fixation to sopie inorganic thing, as in the case of the barnacles, is
therefore seen to operate iA the direction .of producing degeneration
of the animal's constitution. The tendency of such habit is toward
simplification of structure and not toward that progressive advance
and evolution which, in the case of the higher crustacean races, have
evolved from the relatively simple " nauplius " of the past the crabs,
lobsters, shrimps, and prawns of to-day. — Gentleman's Magazine.
\^To be continued.']



THE PRIMEVAL AMERICAIN" COXTIXENT.

Bt L. r. GRATACAP, A. M.

THE reader may recall standing, when a child, by the side of a
toy-dam in the course of some little stream, and, were a breach
made in the mimic masonry, remember the mute interest with Avhich
he watched the slow emergence of fairy islands as points of rock and
shoals of mud slowly appeared above the water's surface — how the
detached summits, at first round spots, assumed varied outlines in-
dented with cones or bristling with promontories ; how they multi-
plied as the ebbing water exposed newer and lower levels, until the



230 THE POPULAR SCIENCE MONTHLY.

tiny sea was dotted with an archiiDelago of islands, whose nearing
shores, gradually joining, formed chains of islets ; how the inclosed
area of water contracted, and, in the union of all their separate figures,
vanished. The wet surfaces, broken by depressions, were marked by
pits of water from whose sides stole along intermediate creases, thread-
like lines of water, the river system of the miniature continent, its
sinuous shores impressed by the ripples of a mimic sea. The recollec-
tion of boyish pleasures becomes touched with a deeper interest when
one is taught to recognize in this the picture of what in a larger way,
and under cosmic conditions, has happened in the life-history of our
own sphere, and to realize that his childish hand may have repro-
duced at will a somewhat exact copy of the stages of the world's
growth.

Suppose this little world so briefly made had been left till the
bright sunshine -had dried its surface, in some places parched and
cracked it, in others evoked a luxuriant growth of grass and flowers,
filled its shores with gliding snails and its level mead with teeming
ant-hills. Once more the running stream is stopped, and slowly the
muddy tide rises higher and higher, obliterates the lowlands and
creeps slowly up the sides of the high ground, around the skirts of
its pygmy mountain-chains, and rolls restored amid groups of remade
islets. Under the guidance of this retrospective knowledge let the
current be arrested to permit some portions of that first-made land
to remain uncovered. With favorable condition^ as a stream car-
rying abundance of fine silt, the water moving sluggishly over the
inundated surfaces will droj) its earthy burden upon them in thin,
loose layers, evenly at first, but, as shallows are formed, irregularly
modified, or as sudden freshets produce stronger currents, eddies and
ripple-bars gather or disturb the sediment. New lands in wet banks
and knobs will begin to appear over the highest ridges. Break away
again the barrier, and cause the water to recede, exposing in a simi-
lar succession of phases the bared surface. The expectant eye now
notices certain changes : old landmarks are removed from sight, val-
leys have been converted into plains, new hills have arisen, lakes
are seen here and there where before was dry land, new contour lines
surround the structural ridges which yet remain, modified indeed, but
distinctly recognizable, while the low verdure of grass and the numer-
ous pinnacles of ant-hills have together disappeared beneath a uni-
versal blanket of mud. Only upon the very highest points do the
scattered remnants of the first surface appear unchanged, because they
alone were exempted from general flood. Again the sun shines upon
it, new seeds sprout, other insects flourish, and fresh showers fall. In
spots the old land is exposed ; the new having been washed away
from it ; it may be easily recognized by its fauna and flora, the
drowned ants, and the hidden grass.

Again and again, under varying conditions, may our experimental



THE PRIMEVAL AMERICAN CONTINENT. 231

world be sunk and raised, preserving, possibly, through all the changes
the rudimentary outlines of hills and valleys by which it was first
characterized and marked. And imagining that every new stratum
was ingeniously varied in the color and to some extent in the nat-
ure of its mineral constituents, and that, upon each reappearance of
this diminutive continent, the skillful experimentalist spread a new
form of life, what at last might be, after some exposure to weather-
ing and change, the character of its surface ? Evidently something
like this : in the first place, since, in consequence partly of denudation
and partly of only partial submergence, certain tracts will appear
cleared of the later deposits, we will find numbers of the whole series
laid bare in spots from the highest point, where, as presupposed, only
the primitive layer is seen, to the outskirts of the island where the lat-
est layer forms the surface ; or to interior depressions, where lake-like
centers existed alternately filled and emptied with each recurring del-
uge. Endless diversity might be introduced into such a scheme, so far
as local detail is concerned, but under the conditions given the island
would exhibit lines of stratification, each distinguished by color or
fossils, and following each other in the order instituted by the youth-
ful world-makers. Along the crevices and tiny gullies we might
detect the minute succession of various strata, and at intervals • frag-
ments of the buried life would be revealed. Enlarge this minute
illustration till it assumes continental dimensions, reverse the periodic
inundations from^the water rising to periodic inundations from the
land sinking, and in a rude way, subject to important modifications,
the reader will be prepared to realize the formative system developed
in the construction of our northern hemisphere.

Through a sequence of phases, somewhat distinctively bounded by
periods of depression and consequent submergence, and periods of ele-
vation and consequent drainage, land was added to an initial nucleus by
enormous marine accumulations, tbe debris of animal organisms, and
the detritus from terrestrial abrasion. Chemical action, heat, and
molecular transference hardened these layers into stone, and thus the
new-made land, though undergoing change from recurring submer-
gence, and through subaerial denudation, yet, to a great extent, re-
sisted removal while it contributed to the growth of the incipient
continent, and formed the ground upon which new-laid strata "<^'ere
heaped.

In the American ^Museum of Natural History, seven maps, the work
of Professor R. P. Whitfield, have recently been added to the Geologi-
cal Cabinet, intended to exhibit the growth of the eastern half of the
North American Continent from 95° west longitude eastward to its
shores. The scheme of their arrangement is the exhibition, by con-
trasted colors, of the superficial areas where to-day the rocks of the
various geological epochs are exposed, beginning with the oldest and
rising to the youngest, whereby we seem to seize at critical points the



232 THE POPULAR SCIE^'CE MONTHLY.

stages of the continent's enlargement, and follow Avith the eye tlu
stupendous changes which shaped it.

The first chart presents in its colored parts the primeval territory,
which geologists regard as the first-made land of our continent, the
archaic regions, around whose rocky framework were gathered the ac-
cretions of succeeding ages. It is the azoic terrain, that composite
foundation of gneiss, granite, schists, crystalline limestones, sandstones,
serpentine, and iron-ore masses, which defined the geological archi-
tecture of America. In its isolated ridges, cleared of the later and
adjacent strata, we have before our eyes the principal portions of a
continent upon which the ancient oceans played

"... their priest-like task
■• Of pure ablution round earth's lifeless shores."

Its sterile stretches unalleviated by a mantle of waving woods, unani-
raated by moving figures, reflected the harsh sunshine from rugged
terraces or monotonous lowlands, a cheerless waste bathed by j)re-
adamite seas.

Starting from a point near Montgomery, in Alabama, the archrean
country stretches northeasterly along the Appalachian axis and, rap-
idly widening, incloses large districts in Georgia, western South and
North Carolina, of which latter State it defines the western boundary,
and i-eaches eastward nearly to Raleigh. Passing on both sides of n
lenticular area lying in North Carolina and Virginia, it narrows to a
strip west of Richmond, where it is deeply bitten by a round gulf, and
pressed to the seaboard, forms a thin isthmus west of Washington, then
expands at Baltimore, and, lobed out into a pennant-shaped appendage,
reaches down toward Newcastle, Delaware. From a little west of
Burlington, nearly to Easton, a white patch shows an area where the
archean rock is no longer seen, but at the latter point a thin strip
follows the Appalachian uplift and, including the highlands of West
Point, appears as an attenuated finger or arm of a great area, which
pushes south as far as Manhattan Island, whose gneissoid rocks com-
pose it, and eastward over the western half of Connecticut. In Mas-
sachusetts the archaean rocks bifurcate ; a finger reaches to the northern
boundary of the State, where a thin connection exists with the great
eastern region, and a shrunken area extends northward through the
Berkshire Hills. The western limit of this latter strip lies some ten
or fifteen miles from the eastern boundary of New York, and, entering
Vermont at its southeastern border, widens out till, at Montpelier, al-
most half the State is covered. Slowly broadening thence, we follow
its outlines into Canada, approach the St. Lawrence, and then, with an
abrupt eastward deflection, trace it in a sinuous tongue until it touches
the river at Mount Camille. The large eastern seaboard area of ar-
chaean rocks commences at Saybrook, on Long Island Sound, whence
northward, limited by a sweeping curve, it covers the eastern part of



THE PRIMEVAL AMERICAN COXTIXEXT. 233

Connecticut, almost all of Rhode Island, and eastern Massachusetts,
with some slight exceptions, where islands of later rock occur, as
southwest from Boston and about Lowell. Nearly all New Hamp-
shire is covered by it, and in Canada it forms another strip parallel
to the first, while eastward it constitutes the surface rock of much
of Maine, wherein, at last, it breaks up into scattered patches, lying
like Titanic stepping-stones, from Augusta northward to the desolate
horn of Newfoundland. One of these districts surrounds Mount Ka-
tahdin ; another, in a long, easterly-deflected strip of land, runs from
Mount Desert northward to Chaleur Bay, New Brunswick ; while from
Machias Bay a third streams northward in a narrow ribbon.

Separated areas are found along the southern shore of Newfound-
land and upon Cape Breton Island.

In the United States four other extensive archcean territories exist
east of 95° west longitude ; one in the Adirondack region, embracing
the immense northern park of New Xork as far north as Malone, and
stretching southward almost to Saratoga Springs, bordered by the
State line, and, linking, through a narrow aperture between surfaces of
subsequent strata, with the enormous reaches of azoic land which form
Quebec and Ontario Provinces, it merges into two lateral expansions,
on one side into the limitless highlands of Labrador, on the other into
the ridges, valleys, and plateaus of the lake country northward to the
Arctic Circle.

The second area is in northern "Wisconsin and Michigan, embracing
the Marquette region, famous for its ores. The third is a neighboring
and related province in eastern Minnesota, from the South Bend on
the Minnesota River, widening northward and uniting with the Cana-
dian area about the Rainy Lake region. The fourth, a diminutive
outlier, comprises the Iron Mountain and Pilot Knob country in south-
east Missouri.

Tliese large spaces of archnean rock represent the floor-layers, as
now exposed in the eastern United States, of the continent's super-
structure. In these parts of our country they form the surface-rock,
and whether they have been always raised beyond the reach of sedi-
mentary deposit or have been scoured and relieved by frost and flood
of superincumbent strata, whether their present extent is conterminous
with their limits, as once revealed above the level of primeval seas, or
whether shrunken by subsidence and partially obliterated by later
formations, they are at any rate outcrops of the vast bedding on which
ocean and continent alike repose. But when we examine these aged
stones we find that they themselves appear as the cemented residues
and stratified deposits formed from some yet preiixistent firmament of
land. In serial bands, conforming to each other, as book lies against
book, we find limestone, slates, sandstones, quartzites, schists, and
gneiss, and we know now that these regular layei-s, hard, distinct, and
characterized by color, constituents, and adventitious minerals, were



234 ^^^ POPULAR SCIEXCE MONTHLY.

once water-drifted beds metamorphosed, transfigured, as it were, by
heat and pressure into this adamantine pavement ; and, further, we
find that they must have been so formed in the attrition and decay
of yet older continents. The dim perspective opens backward to the
very verge of chaos.

After deposition, and in a somewhat consolidated state, they were
sloAvly raised, their emergence aboA^e the water accompanied a contrac-
tion of the earth's crust, and the flexible series, from top to bottom,
folded up in deep and multiplied plications. Mountain-chains arose,
their strata tilted up, contorted and complicated in related groups of
synclinal and anticlinal axes, and, by the effective agency of heat and
aqueous distillation through the myriad pores of the rock, a minera-
logical change ensued. The argillaceous muds were hardened into
slates and schists, the calcareous shoals became crystalline limestones,
marbles, and dolomites, the siliceous bands became quartzites and sand-
stones, the iron slime crystallizecj into colossal sheets of iron-ore, mag-
nesian sediments became serpentine, and through all there developed
beautiful minerals under various associations and marking different
horizons in this complex pile of natural masonry. Feldspars, pyrox-
ene, mica, apatite, chondrodite, epidote, and garnet are a few of many
Avhich, in crevice and seam, and scattered through the matrix rock,
remain as token, and possibly revelation, of the changes here enacted.
From this archaean country come the magnetic oxide of the Adiron-
dacks, the hematite of Marquette, the soft lead of Ticonderoga, the
dolomite of Westchester County, the mica of North Carolina, the sye-
nites and granites of Maine, the marbles of Vermont, the tinstone of
New Hampshire, and the phosphates of Canada. Over thirty thousand
feet in vertical thickness is the estimated depth of this gigantic mass
— fitting foundation for the arches of the world.

Recent study, notably that of Dr. T. Sterry Hunt, separates this
wonderful epoch into four secondary ones of unequal duration and
varying character. First, the Laurentian, a name given by the Geo-
logical Survey of Canada and applied originally to the rocks of the
Laurentian highlands, those abraded swells of land which overlook the
St. Lawrence and rise in rugged grandeur four thousand feet high
above the shadoAved waters of the Saguenay. This primitive tract of
archrean territory embraces the xidirondacks of New York, the region
about OttaAva, portions of NcAvfoundland, and probably includes the
rock assigned to this age in Massachusetts, Connecticut, and Rhode
Island, and the long back Avhieh makes up the Highlands of the Hud-
son, the South Mountain of Xcav Jersey, and the ridges about Rich-
mond and Mount Roan in North Carolina. The rock is " a strong,
massive gneiss, reddish or grayish in color."

Following this is the Norian, unconformable with the Laurentian,
viz., not fitting into it, as though the latter, first made under water,
solidified and raised, had again been depressed and received these sec-



THE PRIMEVAL AMERICAN CONTINENT. 235

ondary deposits. The Norian rock is distinguished by the abundance
of labradorite, a feldspar possessing iridescent tints, and is found in
Essex County, New York, Labrador, extensively along the St. Law-
rence, upon Lake Huron, while " bowlders of it are occasionally found
along the eastern shores of Maine and Massachusetts, and also in north-
ern New Jersey."

The Iluronian era succeeds, and is a name applied to the upper
layers of the Huron Mountains, Lake Superior, to the Green Mountain
series, and to detached areas along the coast of Newfoundland, east-
ern New England, and southward upon the flanks of the Blue Ridge.
The Mont Alban series marks the fourth period, so named after the
White Mountain layers in New Hampshire, where the aggregated dis-
play of crystalline schist is assigned to this province. New York,
Philadelphia, Baltimore, and Washington occupy this terrain, and
these rocks occur throughout the Blue Ridge, as far as Georgia, of
more than passing significance, as they form the gold-bearing strata
i'l Virginia, North and South Carolina. In these rocks the garnet,
staurolite, cyanite, and chiastolite, favorites of the mineralogist, are
almost exclusively found.

Instinctively we ask: Did no living thing exist through all these
ages ; did the mechanical wear and tear of rock-masses and their rede-
position by mechanical means solely occupy the desolate centuries?
The proofs of organic activity, involving the functions of life, are nu-
merous, but the exact character of that life and the special conditions
under which it flourished are greatly if not entirely wanting. In the
first place, we find in Canada important, indeed inexhaustible deposits
of carbon under the form of graphite, and graphite occurs in our coal-
measures as the direct product of alteration from coal. These huge
masses, distributed in pockets, sheets, and nodules through the archtean
rock, indicate the presence of vegetative forces, doubtless exhibited in
plants of a low order, but on a scale of tropical exuberance.

These carbon pockets occupy the shrunken areas of what were once
vast, waving, and deeply matted beds of algse, sea-weeds, building up,
through innumerable generations amid the gathered detritus of shore
and cliff, dense piles of carbonaceous remains. Or else they are attrib-
utable to a fertile growth of lichens which spread, possibly with an



Online LibraryD. S. (David Samuel) MargoliouthThe Popular science monthly (Volume 19) → online text (page 29 of 110)