A. H. Leahy - "Heroic Romances of Ireland Volumes 1 and 2 Combined"

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New Philadelphia Book Publisher Highlights Local Talent
Book and Publishing News from Publishers Newswire(tm)

Looking for Child to be on Cover of a New Book, 'The Model Child'
PHILADELPHIA, Pa. -- The Philadelphia literary world will celebrate the launch of two new players today, April 10th: Kay Square Press, a new publishing company focused on Philadelphia-area artists, their stories, and their art; and Kay Square's first release, 'With the Rich and Mighty: Emlen Etting of Philadelphia' (ISBN: 978-0-9815129-0-7), a critical biography by Kenneth C. Kaleta.

FlatSigned Press Alleges Don Imus Remarks Damage Legacy of President Gerald R. Ford
NEW YORK, N.Y. -- Nathan Yungerberg, an accomplished model scout and professional child photographer is launching a nation-wide casting call to find the cover model for his highly anticipated book release, 'The Model Child: A Parents Guide to the Child Modeling Industry' (ISBN: 978-0-9817018-0-6).

Books: On the Origin of Species

C >> Charles Darwin >> On the Origin of Species




With respect to the almost universal sterility of species when first
crossed, which forms so remarkable a contrast with the almost
universal fertility of varieties when crossed, I must refer the reader
to the recapitulation of the facts given at the end of the eighth
chapter, which seem to me conclusively to show that this sterility is
no more a special endowment than is the incapacity of two trees to be
grafted together, but that it is incidental on constitutional
differences in the reproductive systems of the intercrossed species.
We see the truth of this conclusion in the vast difference in the
result, when the same two species are crossed reciprocally; that is,
when one species is first used as the father and then as the mother.

The fertility of varieties when intercrossed and of their mongrel
offspring cannot be considered as universal; nor is their very general
fertility surprising when we remember that it is not likely that
either their constitutions or their reproductive systems should have
been profoundly modified. Moreover, most of the varieties which have
been experimentised on have been produced under domestication; and as
domestication apparently tends to eliminate sterility, we ought not to
expect it also to produce sterility.

The sterility of hybrids is a very different case from that of first
crosses, for their reproductive organs are more or less functionally
impotent; whereas in first crosses the organs on both sides are in a
perfect condition. As we continually see that organisms of all kinds
are rendered in some degree sterile from their constitutions having
been disturbed by slightly different and new conditions of life, we
need not feel surprise at hybrids being in some degree sterile, for
their constitutions can hardly fail to have been disturbed from being
compounded of two distinct organisations. This parallelism is
supported by another parallel, but directly opposite, class of facts;
namely, that the vigour and fertility of all organic beings are
increased by slight changes in their conditions of life, and that the
offspring of slightly modified forms or varieties acquire from being
crossed increased vigour and fertility. So that, on the one hand,
considerable changes in the conditions of life and crosses between
greatly modified forms, lessen fertility; and on the other hand,
lesser changes in the conditions of life and crosses between less
modified forms, increase fertility.

Turning to geographical distribution, the difficulties encountered on
the theory of descent with modification are grave enough. All the
individuals of the same species, and all the species of the same
genus, or even higher group, must have descended from common parents;
and therefore, in however distant and isolated parts of the world they
are now found, they must in the course of successive generations have
passed from some one part to the others. We are often wholly unable
even to conjecture how this could have been effected. Yet, as we have
reason to believe that some species have retained the same specific
form for very long periods, enormously long as measured by years, too
much stress ought not to be laid on the occasional wide diffusion of
the same species; for during very long periods of time there will
always be a good chance for wide migration by many means. A broken or
interrupted range may often be accounted for by the extinction of the
species in the intermediate regions. It cannot be denied that we are
as yet very ignorant of the full extent of the various climatal and
geographical changes which have affected the earth during modern
periods; and such changes will obviously have greatly facilitated
migration. As an example, I have attempted to show how potent has been
the influence of the Glacial period on the distribution both of the
same and of representative species throughout the world. We are as yet
profoundly ignorant of the many occasional means of transport. With
respect to distinct species of the same genus inhabiting very distant
and isolated regions, as the process of modification has necessarily
been slow, all the means of migration will have been possible during a
very long period; and consequently the difficulty of the wide
diffusion of species of the same genus is in some degree lessened.

As on the theory of natural selection an interminable number of
intermediate forms must have existed, linking together all the species
in each group by gradations as fine as our present varieties, it may
be asked, Why do we not see these linking forms all around us? Why are
not all organic beings blended together in an inextricable chaos? With
respect to existing forms, we should remember that we have no right to
expect (excepting in rare cases) to discover DIRECTLY connecting links
between them, but only between each and some extinct and supplanted
form. Even on a wide area, which has during a long period remained
continuous, and of which the climate and other conditions of life
change insensibly in going from a district occupied by one species
into another district occupied by a closely allied species, we have no
just right to expect often to find intermediate varieties in the
intermediate zone. For we have reason to believe that only a few
species are undergoing change at any one period; and all changes are
slowly effected. I have also shown that the intermediate varieties
which will at first probably exist in the intermediate zones, will be
liable to be supplanted by the allied forms on either hand; and the
latter, from existing in greater numbers, will generally be modified
and improved at a quicker rate than the intermediate varieties, which
exist in lesser numbers; so that the intermediate varieties will, in
the long run, be supplanted and exterminated.

On this doctrine of the extermination of an infinitude of connecting
links, between the living and extinct inhabitants of the world, and at
each successive period between the extinct and still older species,
why is not every geological formation charged with such links? Why
does not every collection of fossil remains afford plain evidence of
the gradation and mutation of the forms of life? We meet with no such
evidence, and this is the most obvious and forcible of the many
objections which may be urged against my theory. Why, again, do whole
groups of allied species appear, though certainly they often falsely
appear, to have come in suddenly on the several geological stages? Why
do we not find great piles of strata beneath the Silurian system,
stored with the remains of the progenitors of the Silurian groups of
fossils? For certainly on my theory such strata must somewhere have
been deposited at these ancient and utterly unknown epochs in the
world's history.

I can answer these questions and grave objections only on the
supposition that the geological record is far more imperfect than most
geologists believe. It cannot be objected that there has not been time
sufficient for any amount of organic change; for the lapse of time has
been so great as to be utterly inappreciable by the human intellect.
The number of specimens in all our museums is absolutely as nothing
compared with the countless generations of countless species which
certainly have existed. We should not be able to recognise a species
as the parent of any one or more species if we were to examine them
ever so closely, unless we likewise possessed many of the intermediate
links between their past or parent and present states; and these many
links we could hardly ever expect to discover, owing to the
imperfection of the geological record. Numerous existing doubtful
forms could be named which are probably varieties; but who will
pretend that in future ages so many fossil links will be discovered,
that naturalists will be able to decide, on the common view, whether
or not these doubtful forms are varieties? As long as most of the
links between any two species are unknown, if any one link or
intermediate variety be discovered, it will simply be classed as
another and distinct species. Only a small portion of the world has
been geologically explored. Only organic beings of certain classes can
be preserved in a fossil condition, at least in any great number.
Widely ranging species vary most, and varieties are often at first
local,--both causes rendering the discovery of intermediate links less
likely. Local varieties will not spread into other and distant regions
until they are considerably modified and improved; and when they do
spread, if discovered in a geological formation, they will appear as
if suddenly created there, and will be simply classed as new species.
Most formations have been intermittent in their accumulation; and
their duration, I am inclined to believe, has been shorter than the
average duration of specific forms. Successive formations are
separated from each other by enormous blank intervals of time; for
fossiliferous formations, thick enough to resist future degradation,
can be accumulated only where much sediment is deposited on the
subsiding bed of the sea. During the alternate periods of elevation
and of stationary level the record will be blank. During these latter
periods there will probably be more variability in the forms of life;
during periods of subsidence, more extinction.

With respect to the absence of fossiliferous formations beneath the
lowest Silurian strata, I can only recur to the hypothesis given in
the ninth chapter. That the geological record is imperfect all will
admit; but that it is imperfect to the degree which I require, few
will be inclined to admit. If we look to long enough intervals of
time, geology plainly declares that all species have changed; and they
have changed in the manner which my theory requires, for they have
changed slowly and in a graduated manner. We clearly see this in the
fossil remains from consecutive formations invariably being much more
closely related to each other, than are the fossils from formations
distant from each other in time.

Such is the sum of the several chief objections and difficulties which
may justly be urged against my theory; and I have now briefly
recapitulated the answers and explanations which can be given to them.
I have felt these difficulties far too heavily during many years to
doubt their weight. But it deserves especial notice that the more
important objections relate to questions on which we are confessedly
ignorant; nor do we know how ignorant we are. We do not know all the
possible transitional gradations between the simplest and the most
perfect organs; it cannot be pretended that we know all the varied
means of Distribution during the long lapse of years, or that we know
how imperfect the Geological Record is. Grave as these several
difficulties are, in my judgment they do not overthrow the theory of
descent with modification.

Now let us turn to the other side of the argument. Under domestication
we see much variability. This seems to be mainly due to the
reproductive system being eminently susceptible to changes in the
conditions of life; so that this system, when not rendered impotent,
fails to reproduce offspring exactly like the parent-form. Variability
is governed by many complex laws,--by correlation of growth, by use
and disuse, and by the direct action of the physical conditions of
life. There is much difficulty in ascertaining how much modification
our domestic productions have undergone; but we may safely infer that
the amount has been large, and that modifications can be inherited for
long periods. As long as the conditions of life remain the same, we
have reason to believe that a modification, which has already been
inherited for many generations, may continue to be inherited for an
almost infinite number of generations. On the other hand we have
evidence that variability, when it has once come into play, does not
wholly cease; for new varieties are still occasionally produced by our
most anciently domesticated productions.

Man does not actually produce variability; he only unintentionally
exposes organic beings to new conditions of life, and then nature acts
on the organisation, and causes variability. But man can and does
select the variations given to him by nature, and thus accumulate them
in any desired manner. He thus adapts animals and plants for his own
benefit or pleasure. He may do this methodically, or he may do it
unconsciously by preserving the individuals most useful to him at the
time, without any thought of altering the breed. It is certain that he
can largely influence the character of a breed by selecting, in each
successive generation, individual differences so slight as to be quite
inappreciable by an uneducated eye. This process of selection has been
the great agency in the production of the most distinct and useful
domestic breeds. That many of the breeds produced by man have to a
large extent the character of natural species, is shown by the
inextricable doubts whether very many of them are varieties or
aboriginal species.

There is no obvious reason why the principles which have acted so
efficiently under domestication should not have acted under nature. In
the preservation of favoured individuals and races, during the
constantly-recurrent Struggle for Existence, we see the most powerful
and ever-acting means of selection. The struggle for existence
inevitably follows from the high geometrical ratio of increase which
is common to all organic beings. This high rate of increase is proved
by calculation, by the effects of a succession of peculiar seasons,
and by the results of naturalisation, as explained in the third
chapter. More individuals are born than can possibly survive. A grain
in the balance will determine which individual shall live and which
shall die,--which variety or species shall increase in number, and
which shall decrease, or finally become extinct. As the individuals of
the same species come in all respects into the closest competition
with each other, the struggle will generally be most severe between
them; it will be almost equally severe between the varieties of the
same species, and next in severity between the species of the same
genus. But the struggle will often be very severe between beings most
remote in the scale of nature. The slightest advantage in one being,
at any age or during any season, over those with which it comes into
competition, or better adaptation in however slight a degree to the
surrounding physical conditions, will turn the balance.

With animals having separated sexes there will in most cases be a
struggle between the males for possession of the females. The most
vigorous individuals, or those which have most successfully struggled
with their conditions of life, will generally leave most progeny. But
success will often depend on having special weapons or means of
defence, or on the charms of the males; and the slightest advantage
will lead to victory.

As geology plainly proclaims that each land has undergone great
physical changes, we might have expected that organic beings would
have varied under nature, in the same way as they generally have
varied under the changed conditions of domestication. And if there be
any variability under nature, it would be an unaccountable fact if
natural selection had not come into play. It has often been asserted,
but the assertion is quite incapable of proof, that the amount of
variation under nature is a strictly limited quantity. Man, though
acting on external characters alone and often capriciously, can
produce within a short period a great result by adding up mere
individual differences in his domestic productions; and every one
admits that there are at least individual differences in species under
nature. But, besides such differences, all naturalists have admitted
the existence of varieties, which they think sufficiently distinct to
be worthy of record in systematic works. No one can draw any clear
distinction between individual differences and slight varieties; or
between more plainly marked varieties and sub-species, and species.
Let it be observed how naturalists differ in the rank which they
assign to the many representative forms in Europe and North America.

If then we have under nature variability and a powerful agent always
ready to act and select, why should we doubt that variations in any
way useful to beings, under their excessively complex relations of
life, would be preserved, accumulated, and inherited? Why, if man can
by patience select variations most useful to himself, should nature
fail in selecting variations useful, under changing conditions of
life, to her living products? What limit can be put to this power,
acting during long ages and rigidly scrutinising the whole
constitution, structure, and habits of each creature,--favouring the
good and rejecting the bad? I can see no limit to this power, in
slowly and beautifully adapting each form to the most complex
relations of life. The theory of natural selection, even if we looked
no further than this, seems to me to be in itself probable. I have
already recapitulated, as fairly as I could, the opposed difficulties
and objections: now let us turn to the special facts and arguments in
favour of the theory.

On the view that species are only strongly marked and permanent
varieties, and that each species first existed as a variety, we can
see why it is that no line of demarcation can be drawn between
species, commonly supposed to have been produced by special acts of
creation, and varieties which are acknowledged to have been produced
by secondary laws. On this same view we can understand how it is that
in each region where many species of a genus have been produced, and
where they now flourish, these same species should present many
varieties; for where the manufactory of species has been active, we
might expect, as a general rule, to find it still in action; and this
is the case if varieties be incipient species. Moreover, the species
of the larger genera, which afford the greater number of varieties or
incipient species, retain to a certain degree the character of
varieties; for they differ from each other by a less amount of
difference than do the species of smaller genera. The closely allied
species also of the larger genera apparently have restricted ranges,
and they are clustered in little groups round other species--in which
respects they resemble varieties. These are strange relations on the
view of each species having been independently created, but are
intelligible if all species first existed as varieties.

As each species tends by its geometrical ratio of reproduction to
increase inordinately in number; and as the modified descendants of
each species will be enabled to increase by so much the more as they
become more diversified in habits and structure, so as to be enabled
to seize on many and widely different places in the economy of nature,
there will be a constant tendency in natural selection to preserve the
most divergent offspring of any one species. Hence during a
long-continued course of modification, the slight differences,
characteristic of varieties of the same species, tend to be augmented
into the greater differences characteristic of species of the same
genus. New and improved varieties will inevitably supplant and
exterminate the older, less improved and intermediate varieties; and
thus species are rendered to a large extent defined and distinct
objects. Dominant species belonging to the larger groups tend to give
birth to new and dominant forms; so that each large group tends to
become still larger, and at the same time more divergent in character.
But as all groups cannot thus succeed in increasing in size, for the
world would not hold them, the more dominant groups beat the less
dominant. This tendency in the large groups to go on increasing in
size and diverging in character, together with the almost inevitable
contingency of much extinction, explains the arrangement of all the
forms of life, in groups subordinate to groups, all within a few great
classes, which we now see everywhere around us, and which has
prevailed throughout all time. This grand fact of the grouping of all
organic beings seems to me utterly inexplicable on the theory of
creation.

As natural selection acts solely by accumulating slight, successive,
favourable variations, it can produce no great or sudden modification;
it can act only by very short and slow steps. Hence the canon of
"Natura non facit saltum," which every fresh addition to our knowledge
tends to make more strictly correct, is on this theory simply
intelligible. We can plainly see why nature is prodigal in variety,
though niggard in innovation. But why this should be a law of nature
if each species has been independently created, no man can explain.

Many other facts are, as it seems to me, explicable on this theory.
How strange it is that a bird, under the form of woodpecker, should
have been created to prey on insects on the ground; that upland geese,
which never or rarely swim, should have been created with webbed feet;
that a thrush should have been created to dive and feed on sub-aquatic
insects; and that a petrel should have been created with habits and
structure fitting it for the life of an auk or grebe! and so on in
endless other cases. But on the view of each species constantly trying
to increase in number, with natural selection always ready to adapt
the slowly varying descendants of each to any unoccupied or
ill-occupied place in nature, these facts cease to be strange, or
perhaps might even have been anticipated.

As natural selection acts by competition, it adapts the inhabitants of
each country only in relation to the degree of perfection of their
associates; so that we need feel no surprise at the inhabitants of any
one country, although on the ordinary view supposed to have been
specially created and adapted for that country, being beaten and
supplanted by the naturalised productions from another land. Nor ought
we to marvel if all the contrivances in nature be not, as far as we
can judge, absolutely perfect; and if some of them be abhorrent to our
ideas of fitness. We need not marvel at the sting of the bee causing
the bee's own death; at drones being produced in such vast numbers for
one single act, and being then slaughtered by their sterile sisters;
at the astonishing waste of pollen by our fir-trees; at the
instinctive hatred of the queen bee for her own fertile daughters; at
ichneumonidae feeding within the live bodies of caterpillars; and at
other such cases. The wonder indeed is, on the theory of natural
selection, that more cases of the want of absolute perfection have not
been observed.

The complex and little known laws governing variation are the same, as
far as we can see, with the laws which have governed the production of
so-called specific forms. In both cases physical conditions seem to
have produced but little direct effect; yet when varieties enter any
zone, they occasionally assume some of the characters of the species
proper to that zone. In both varieties and species, use and disuse
seem to have produced some effect; for it is difficult to resist this
conclusion when we look, for instance, at the logger-headed duck,
which has wings incapable of flight, in nearly the same condition as
in the domestic duck; or when we look at the burrowing tucutucu, which
is occasionally blind, and then at certain moles, which are habitually
blind and have their eyes covered with skin; or when we look at the
blind animals inhabiting the dark caves of America and Europe. In both
varieties and species correlation of growth seems to have played a
most important part, so that when one part has been modified other
parts are necessarily modified. In both varieties and species
reversions to long-lost characters occur. How inexplicable on the
theory of creation is the occasional appearance of stripes on the
shoulder and legs of the several species of the horse-genus and in
their hybrids! How simply is this fact explained if we believe that
these species have descended from a striped progenitor, in the same
manner as the several domestic breeds of pigeon have descended from
the blue and barred rock-pigeon!

On the ordinary view of each species having been independently
created, why should the specific characters, or those by which the
species of the same genus differ from each other, be more variable
than the generic characters in which they all agree? Why, for
instance, should the colour of a flower be more likely to vary in any
one species of a genus, if the other species, supposed to have been
created independently, have differently coloured flowers, than if all
the species of the genus have the same coloured flowers? If species
are only well-marked varieties, of which the characters have become in
a high degree permanent, we can understand this fact; for they have
already varied since they branched off from a common progenitor in
certain characters, by which they have come to be specifically
distinct from each other; and therefore these same characters would be
more likely still to be variable than the generic characters which
have been inherited without change for an enormous period. It is
inexplicable on the theory of creation why a part developed in a very
unusual manner in any one species of a genus, and therefore, as we may
naturally infer, of great importance to the species, should be
eminently liable to variation; but, on my view, this part has
undergone, since the several species branched off from a common
progenitor, an unusual amount of variability and modification, and
therefore we might expect this part generally to be still variable.
But a part may be developed in the most unusual manner, like the wing
of a bat, and yet not be more variable than any other structure, if
the part be common to many subordinate forms, that is, if it has been
inherited for a very long period; for in this case it will have been
rendered constant by long-continued natural selection.