21 SEPTEMBER 1945, Page 12

BIRD BEHAVIOUR " Sm,—Mr. A. F. C. Hillstead replied (in

your issue of September 7) to my review of his book The Blackbird. It is clear that while he and I may share each other's respect, we do not share the same views on the nature of evidence, or on the question : with whom does the onus of proof of a statement rest? Nor are we likely to agree as to which of us, in review or counter-review, has missed what point. I do not quite under- stand what Mr. Hillstead means about my contemporaries, their work, their jargon, or their degrees ; or why he thinks I have made any endocrinological studies ; or what litmus paper has to do, or could have