forward, how and why it is that a long isolated form should almost always become slightly modified. I do not know whether you will care about hearing my further opinion on the point in question, for as before remarked I have not attended much of late years to such questions, thinking it prudent, now that I am growing old, to work at easier subjects. Believe me, yours very sincerely, CH. DARWIN. I hope and trust that you will throw light on these points. P.S.--I will add another remark which I remember occurred to me when I first read M. Wagner. When a species first arrives on a small island, it will probably increase rapidly, and unless all the individuals change instantaneously (which is improbable in the highest degree), the slowly, more or less, modifying offspring must intercross one with another, and with their unmodified parents, and any offspring not as yet modified. The case will then be like that of domesticated animals which have slowly become modified, either by the action of the external conditions or by the process which I have called the UNCONSCIOUS SELECTION by man--i.e., in contrast with methodical selection. [The letters continue the history of the year 1872, which has been interrupted by a digression on Isolation.] CHARLES DARWIN TO THE MARQUIS DE SAPORTA. Down, April 8, 1872. Dear Sir, I thank you very sincerely and feel much honoured by the trouble which you have taken in giving me your reflections on the origin of Man. It gratifies me extremely that some parts of my work have interested you, and that we agree on the main conclusion of the derivation of man from some lower form.