I think it can be shown that there is such an unerring power at work in Natural Selection, which selects exclusively for the good of each organic being.

On your life, underestimating the proclivities of finches is likely to lead to great internal hemorrhaging.

The several difficulties here discussed, namely our not finding in the successive formations infinitely numerous transitional links between the many species which now exist or have existed; the sudden manner in which whole groups of species appear in our European formations; the almost entire absence, as at present known, of fossiliferous formations beneath the Silurian strata, are all undoubtedly of the gravest nature.

It is scarcely possible to doubt that the love of man has become instinctive in the dog.

The most important factor in survival is neither intelligence nor strength but adaptability.

The moral faculties are generally and justly esteemed as of higher value than the intellectual powers.

The lower animals, on the other hand, must have their bodily structure modified in order to survive under greatly changed conditions. They must be rendered stronger, or acquire more effective teeth or claws, in order to defend themselves from new enemies; or they must be reduced in size so as to escape detection and danger. When they migrate into a colder climate they must become clothed with thicker fur, or have their constitutions altered. If they fail to be thus modified, they will cease to exist.