Letter from David Keilin, on a paper 'A study of the physical and chemical properties of the insect cuticle' by Gottfried Fraenkel and K M Rudall He finds the new paper more interesting than the original, shorter one. The Royal Society Archives should not be burdened with the MS, as it is the author's duty to look after this. A few modifications could still made. If William Bragg and Dr Astbury are satisfied with the shorter version, then he will not object to it's publication. [Published in Proceedings of the Royal Society A, 1940]. 1 March 1940