Few who are familiar with the facts that genetic research has revealed are now inclined to speculate as to the manner by which the process [species come into existence] has been accomplished. Our knowledge of the nature and properties of living things is far too meagre to justify any such attempts. Suggestions of course can be made: though, however, these ideas may have a stimulating value in the lecture room, they look weak and thin when set out in print.

Preface - Problems In Genetics (1913)