"I have now read the book which you so kindly sent me, but I am very much handicapped by ignorance of the subject. I should say, a priori, it is bound to be right. ... What I should have liked, somewhere, is a sample case of a problem soluble on your principles but not on old-fashioned Darwinian principles. ... I found your book exceedingly interesting and I wish, very strongly, that I had more biological knowledge...."