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the bond of union of their parts and their past history； he finds
himself； according to the received notions； in a mighty maze； and with；
at most； the dimmest adumbration of a plan。 If he starts with any one
clear conviction； it is that every part of a living creature is
cunningly adapted to some special use in its life。 Has not his Paley
told him that that seemingly useless organ； the spleen； is beautifully
adjusted as so much packing between the other organs？ And yet； at the
outset of his studies； he finds that no adaptive reason whatsoever can
be given for one…half of the peculiarities of vegetable structure； he
also discovers rudimentary teeth； which are never used； in the gums of
the young calf and in those of the foetal whale； insects which never
bite have rudimental jaws； and others which never fly have rudimental
wings； naturally blind creatures have rudimental eyes； and the halt
have rudimentary limbs。 So； again； no animal or plant puts on its
perfect form at once； but all have to start from the same point；
however various the course which each has to pursue。 Not only men and
horses； and cats and dogs； lobsters and beetles； periwinkles and
mussels； but even the very sponges and animalcules commence their
existence under forms which are essentially undistinguishable； and this
is true of all the infinite variety of plants。 Nay； more； all living
beings march side by side along the high road of development； and
separate the later the more like they are； like people leaving church；
who all go down the aisle； but having reached the door some turn into
the parsonage； others go down the village； and others part only in the
next parish。 A man in his development runs for a little while parallel
with； though never passing through； the form of the meanest worm； then
travels for a space beside the fish； then journeys along with the bird
and the reptile for his fellow travellers； and only at last； after a
brief companionship with the highest of the four…footed and four…handed
world； rises into the dignity of pure manhood。 No competent thinker of
the present day dreams of explaining these indubitable facts by the
notion of the existence of unknown and undiscoverable adaptations to
purpose。 And we would remind those who； ignorant of the facts； must be
moved by authority； that no one has asserted the incompetence of the
doctrine of final causes； in its application to physiology and anatomy；
more strongly than our own eminent anatomist； Professor Owen； who；
speaking of such cases； says （'On the Nature of Limbs'； pp。 39； 40）： 〃I
think it will be obvious that the principle of final adaptations fails
to satisfy all the conditions of the problem。〃
But； if the doctrine of final causes will not help us to comprehend the
anomalies of living structure； the principle of adaptation must surely
lead us to understand why certain living beings are found in certain
regions of the world and not in others。 The palm； as we know； will not
grow in our climate； nor the oak in Greenland。 The white bear cannot
live where the tiger thrives； nor 'vice versa'； and the more the
natural habits of animal and vegetable species are examined； the more
do they seem； on the whole； limited to particular provinces。 But when
we look into the facts established by the study of the geographical
distribution of animals and plants it seems utterly hopeless to attempt
to understand the strange and apparently capricious relations which
they exhibit。 One would be inclined to suppose 'a priori' that every
country must be naturally peopled by those animals that are fittest to
live and thrive in it。 And yet how； on this hypothesis； are we to
account for the absence of cattle in the Pampas of South America； when
those parts of the New World were discovered？ It is not that they were
unfit for cattle； for millions of cattle now run wild there； and the
like holds good of Australia and New Zealand。 It is a curious
circumstance； in fact； that the animals and plants of the Northern
Hemisphere are not only as well adapted to live in the Southern
Hemisphere as its own autochthones； but are in many cases absolutely
better adapted； and so overrun and extirpate the aborigines。 Clearly；
therefore； the species which naturally inhabit a country are not
necessarily the best adapted to its climate and other conditions。 The
inhabitants of islands are often distinct from any other known species
of animal or plants （witness our recent examples from the work of Sir
Emerson Tennent； on Ceylon）； and yet they have almost always a sort of
general family resemblance to the animals and plants of the nearest
mainland。 On the other hand； there is hardly a species of fish； shell；
or crab common to the opposite sides of the narrow isthmus of Panama。
Wherever we look； then； living nature offers us riddles of difficult
solution； if we suppose that what we see is all that can be known of it。
But our knowledge of life is not confined to the existing world。
Whatever their minor differences； geologists are agreed as to the vast
thickness of the accumulated strata which compose the visible part of
our earth； and the inconceivable immensity of the time of whose lapse
they are the imperfect； but the only accessible witnesses。 Now；
throughout the greater part of this long series of stratified rocks are
scattered； sometimes very abundantly； multitudes of organic remains；
the fossilized exuviae of animals and plants which lived and died while
the mud of which the rocks are formed was yet soft ooze； and could
receive and bury them。 It would be a great error to suppose that these
organic remains were fragmentary relics。 Our museums exhibit fossil
shells of immeasurable antiquity； as perfect as the day they were
formed； whole skeletons without a limb disturbednay； the changed
flesh； the developing embryos； and even the very footsteps of primieval
organisms。 Thus the naturalist finds in the bowels of the earth
species as well defined as； and in some groups of animals more numerous
than； those that breathe the upper air。 But； singularly enough； the
majority of these entombed species are wholly distinct from those that
now live。 Nor is this unlikeness without its rule and order。 As a
broad fact； the further we go back in time the less the buried species
are like existing forms； and the further apart the sets of extinct
creatures are the less they are like one another。 In other words；
there has been a regular succession of living beings； each younger set
being in a very broad and general sense somewhat more like those which
now live。
It was once supposed that this succession had been the result of vast
successive catastrophes； destructions； and re…creations 'en masse'； but
catastrophes are now almost eliminated from geological； or at least
palaeontological speculation； and it is admitted on all hands that the
seeming breaks in the chain of being are not absolute； but only relative
to our imperfect knowledge； that species have replaced species； not in
assemblages； but one by one； and that； if it were possible to have all
the phenomena of the past presented to us； the convenient epochs and
formations