It is, therefore, of the highest importance to gain a clear insight into the means of modification and coadaptation.

At the commencement of my observations it seemed to me probable that a careful study of domesticated animals and of cultivated plants would offer the best chance of making out this obscure problem.

Nor have I been disappointed; in this and in all other perplexing cases I have invariably found that our knowledge, imperfect though it be, of variation under domestication, afforded the best and safest clue.

I may venture to express my conviction of the high value of such studies, although they have been very commonly neglected by naturalists.