on leaves, as because it could not get food any other way--but still, even in these cases the desire may be said to exist, though it is secondary--being founded upon another and more elementary desire--the desire namely of escaping pain or obtaining food. In either case a desire of some kind is a precedent condition of the new action. And so as we know of no case of a new action coming into play without being preceded by desire, we seem to be justified in supposing that all our actions when they were first initiated (in our forefathers, if not in ourselves) were so preceded. If this is so, then, since function is always preceded by desire, and organisation is preceded by function, organisation must necessarily be preceded by desire. And if this is the order of creation in man, should we not reasonably look in this direction for the key to the variation of animals and the order of creation in general?[39] If a farmer's son is occasionally born who hates farming and loves music, and who ultimately through the force of his desire (driving him into oppositions and difficulties and penurious struggles) transforms himself into a musician, is it not also likely that occasionally an animal is born who hates the customs of his tribe, and at last (also through struggles) transforms himself into something else? Even if he does not succeed (the animal) in entirely transforming himself, he likely transmits the desire in some degree to his descendants, and the transformation is thus carried on and completed later. For everywhere among the animals there _is_ desire, of some kind or another, obviously acting; and if in man, by our own experience, desire is the precursor and first expression of growth, is there any reason why it should not also be so among animals? Lamarck gives the instance--among others--of a gasteropod; how the need or desire of touching bodies in front of it as it crawled along would result in the formation of tentacles. The gasteropod, he says, would keep making efforts to feel with the front of its head, and the determination of consciousness that way would be accompanied by a supply of nervous and other fluids, which would nourish the part and cause growth there--the _form_ of the growth continuing in the same way to be determined by need--till at last two or more tentacles would appear. True, the inward determinations of consciousness may not be so vivid and varied in animals as they are in men; but they are persistent, and by the very cumulative force of habit which is so strong in animals, must at length penetrate down through function into organisation and external form. Who shall say that the lark, by the mere love of soaring and singing in the face of the sun, has not altered the shape of its wings, or that the forms of the shark or of the gazelle are not the long-stored results of character leaning always in certain directions, as much as the forms of the miser or the libertine are among men?