The subject which is treated in this book has occupied my thoughts for ten years or more, but I have refrained from publishing my views, as I hope that I may some time be able to submit them to the test of experiment.
Many experiments have suggested themselves to me, but as most of them involve the cultivation and hybridization, for many generations, of such animals and plants as will thrive and multiply in confinement, they can only be carried out by some one who has the means for experimental researches, and who has also a permanent home in the country, where organisms of many kinds may be kept under observation for years, and where many specimens of hybrids between various wild and domesticated species can be reared to maturity.
My own studies have been in a different province of natural science, and it has therefore seemed best to publish this volume in order to call renewed attention. to this most fascinating subject.
I have little hope that my views will be permanently accepted in the form in which they are here presented, but I do hope that they may serve to bind together and