The law alluded to is thus stated by Wallace: "Every species has come into existence coincident both in space and time with a pre-existing closely allied species" (loc.cit., page 186).); and I have added that I know from correspondence that your explanation of your law is the same as that which I offer.

You are right, that I came to the conclusion that selection was the principle of change from the study of domesticated productions; and then, reading Malthus, I saw at once how to apply this principle.

Geographical distribution and geological relations of extinct to recent inhabitants of South America first led me to the subject: especially the case of the Galapagos Islands.

I hope to go to press in the early part of next month.

It will be a small volume of about five hundred pages or so.