Mr. Darwin has always maintained that the effects of use and disuse are highly important in the development of structure, and if, as he has said, habits are sometimes inherited—then they should sometimes be important also in the development of instinct, or habit. But what does the development of an instinct or structure, or, indeed, any effect upon the organism produced by “use and disuse,” imply? It implies an effect produced by a desire to do something for which the organism was not originally well adapted or sufficient, but for which it has come to be sufficient in consequence of the desire. The wish has been father to the power; but this again opens up the whole theory of Lamarck, that the development of organs has been due to the wants or desires of the animal in which the organ appears. So far as I can see, I am insisting on little more than this.
Once grant that a blacksmith’s arm grows thicker through hammering iron, and you have an organ modified in accordance with a need or wish. Let the desire and the practice be remembered, and go on for long enough, and the slight alterations of the organ will be accumulated, until they are checked either by the creature’s having got all that he cares about making serious further effort to obtain, or until his wants prove inconvenient to other creatures that are stronger than he, and he is hence brought to a standstill. Use and disuse, then, with me, and, as I gather also, with Lamarck, are the keys to the position, coupled, of course, with continued personality and memory. No sudden and striking changes would be effected, except that occasionally a blunder might prove a happy accident, as happens not unfrequently with painters, musicians, chemists, and inventors at the present day; or sometimes a creature, with exceptional powers of memory or reflection, would make his appearance in this race or in that. We all profit by our accidents as well as by our more cunning contrivances, so that analogy would point in the direction of thinking that many of the most happy thoughts in the animal and vegetable kingdom were originated much as certain discoveries that have been made by accident among ourselves. These would be originally blind variations, though even so, probably less blind than we think, if we could know the whole truth. When originated, they would be eagerly taken advantage of and improved upon by the animal in whom they appeared; but it cannot be supposed that they would be very far in advance of the last step gained, more than are those “flukes” which sometimes enable us to go so far beyond our own ordinary powers. For if they were, the animal would despair of repeating them. No creature hopes, or even wishes, for very much more than he has been accustomed to all his life, he and his family, and the others whom he can understand, around him. It has been well said that “enough” is always “a little more than one has.” We do not try for things which we believe to be beyond our reach, hence one would expect that the fortunes, as it were, of animals should have been built up gradually. Our own riches grow with our desires and the pains we take in pursuit of them, and our desires vary and increase with our means of gratifying them; but unless with men of exceptional business aptitude, wealth grows gradually by the adding field to field and farm to farm; so with the limbs and instincts of animals; these are but the things they have made or bought with their money, or with money that has been left them by their forefathers, which, though it is neither silver nor gold, but faith and protoplasm only, is good money and capital notwithstanding.