Letter from Conrad Hal Waddington, on a paper 'The effects of antero-posterior reversal of lengths of the primitive streak in the chick' by Michael Abercrombie to D C Martin, Assistant Secretary of the Royal Society Reporting on the paper was an embarrassing task for him as the author had put his discussion in terms of a criticism of a view which was attributed to him. However, it was a view that he had never held. He has expressed an opinion of the paper but another opinion should be sought from Julian Huxley. [Published in Philosophical Transactions B, 1950]. Endorsed on recto as received 19 August 1949. 18 August 1949