Page:Jardine Naturalist's Library Foreign Butterflies.djvu/38

36. It is susceptible of demonstration, that if species had an absolute constancy, there would be no varieties, but naturalists cannot help acknowledging that such exist.

Whatever changes circumstances may have produced in individuals, are all preserved by generation, and transmitted to new individuals emanating from those which have undergone these changes. Unless this were the case, Nature could never have introduced the diversity among animals which we now witness, nor a progression in the composition of their organs and faculties.

Such is Lamarck's theory of life, and manner of accounting for the innumerable variety of forms in which living nature now appears. If his principles were once admitted, they would not only produce the effects he ascribes to them, but it would be a matter of surprise that natural productions are not infinitely more diversified than they really are, for nothing more is necessary than time and circumstances for any one animal form to be transformed into any other,—for a monad or a polypus to become indifferently a frog, an eagle, an elephant, or a man. But the two suppositions on which they rest, viz. that it is the seminal vapour which organizes the embryo, and that efforts and desires engender organs, are both so entirely arbitrary, and the latter so obviously fallacious, that very few have ever thought it worth while to attempt a formal