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and indefinite variations could have brought about such special forms and modifications as have been enumerated in this chapter, seems to contradict not imagination, but
That either many individuals amongst a species of butterfly should be simultaneously preserved through a similar accidental and minute variation in one definite direction, when variations in many other directions would also preserve; or that one or two so varying should succeed in supplanting the progeny of thousands of other individuals, and that this should by no other cause be carried so far as to produce the appearance (as we have before stated) of spots of fungi, &c.--are alternatives of an improbability so extreme as to be practically equal to impossibility.
In spite of all the resources of a fertile imagination, the Darwinian, pure and simple, is reduced to the assertion of a paradox as great as any he opposes. In the place of a mere assertion of our ignorance as to the way these phenomena have been produced, he brings forward as their explanation a cause which, it is contended in this work, is demonstrably insufficient.
Of course here, as elsewhere throughout nature, we have to do with the operation of fixed and constant natural laws, and the knowledge of these may before long be obtained by human patience or human genius. There seems, however, already enough evidence to show that these as yet unknown natural laws will never be resolved into the action of Natural Selection," but will constitute or exemplify a mode and condition of organic action of which the Darwinian theory takes no account whatsoever.
THE CO-EXISTENCE OF CLOSELY SIMILAR STRUCTURES
OF DIVERSE ORIGIN.
- The eye.
Chances against concordant variations. —Examples of discordant ones.
Concordant variations not unlikely on a non-Darwinian evolutionary hypothesis.—Placental and implacental mammals.—Birds and reptiles. – Independent origins of similar sense organs. — The ear. — Other coincidences.—Causes besides “Natural Selection” produce concordant variations, in certain geographical regions. —Causes besides “Natural Selection” produce concordant variations, in certain zoological and botanical groups. - There are homologous parts not genetically related.-Harmony in respect of the organic and inorganic worlds.-Summary and conclusion.
The theory of “ Natural Selection” supposes that the varied forms and structure of animals and plants have been built up merely by indefinite, fortuitous, minute variations in every part and in all directions—those variations only being preserved which are directly or indirectly useful to the individual possessing them, or necessarily correlated with such useful variations.
On this theory the chances are almost infinitely great against the independent accidental occurrence and preservation of two similar series of minute variations resulting
By accidental variations Mr. Darwin does not, of course, mean to imply variations really clue to “chance," but to utterly indeterminate antecedents.
in the independent development of two closely similar forms. In all cases, no doubt (on this same theory), some adaptation to habit or need would gradually be evolved, but that adaptation would surely be arrived at by different roads.
The organic world supplies us with multitudes of examples of similar functional results being attained by the most diverse means. Thus the body is sustained in the air by birds and by bats. In the first case it is so sustained by a limb in which the bones of the hand are excessively reduced, but which is provided with immense outgrowths
WING-BONES OF PTERODACTYLE, BAT, AND BIRD.
from the skin-namely, the feathers of the wing. In the second case, however, the body is sustained in the air by a limb in which the bones of the hand are enormously increased in length, and so sustain a great expanse of naked skin, which is the flying membrane of the bat's wing. Certain fishes and certain reptiles can also flit and take very prolonged jumps in the air. The flying-fish, however takes these by means of a great elongation of the rays of
the pectoral fins-parts which cannot be said to be of the same nature as the constituents of the wing of either the bat or the bird. The little lizard, which enjoys the formidable name of "flying-dragon," flits by means of a structure altogether peculiar—namely, by the liberation and great elongation of some of the ribs which support a fold of skin. In the extinct pterodactyles—which were truly flying rep
tiles—we meet with an approximation to the structure of the bat, but in the pterodactyle we have only one finger elongated in each hand : a striking example of how the very same function may be provided for by a modification similar in principle, yet surely manifesting the independence of its origin. When we go to lower animals, we find flight produced by organs, as the wings of insects, which are not
modified limbs at all; or we may even find the function subserved by quite artificial means, as in the aërial spiders, which use their own threads to float with in the air. In the vegetable kingdom the atmosphere is often made use of for the scattering of seeds, by their being furnished with special structures of very different kinds. The various modes by which sueh seeds are dispersed are well expressed by Mr. Darwin. He says :1 “Seeds are disseminated by their minuteness,-by their capsule being converted into a light balloon-like envelope, — by being embedded in pulp or flesh, formed of the most diverse parts, and rendered nutritious, as well as conspicuously coloured, so as to attract and be devoured by birds,-by having hooks and grapnels of many kinds and serrated awns, so as to adhere to the fur of quadrupeds,—and by being furnished with wings and plumes, as different in shape as elegant in structure, so as to be wafted by every breeze.”
Again, if we consider the poisoning apparatus possessed by different animals, we find in serpents a perforated-or rather very deeply channelled—tooth. In wasps and bees the sting is formed of modified parts, accessory in reproduction. In the scorpion, we have the median terminal process of the body specially organized. In the spider, we have a specially constructed antenna ; and finally, in the centipede a pair of modified thoracic limbs.
It would be easy to produce a multitude of such instances of similar ends being attained by dissimilar means, and it is here contended that by “the action of Natural Selection” only it is so improbable as to be practically impossible for two exactly similar structures to have ever been indepen
Origin of Species,” 5th cuition, p. 235.