|'I beg to acknowledge the receipt of your letter of May 26th. The only illustrations accompanying your paper on the "Co-efficient of diffusion of cells" is a chromus-lithograph plate, which cannot be reproduced cheaply like the ordinary process clocks. The Society does not lend original blocks or plates, so that if you wish for this plate to illustrate your paper it would have to be done over again. [?] it probably nipped off the stone by this time.'