Letter from [Magnus] Gustaf Retzius, Drottninggatan, Stockholm, to Professor [John Rose] Bradford, [Royal Society] Thanking the Royal Society for inviting him to deliver the Croonian Lecture. Points out two difficulties preventing him from immedately accepting: his current workload and selecting a suitable subject for the lecture. He suggests 1. The structure of the central nervous system of the higher and lower animals (including the organs of senses) and 2. The forms and structure of the Spermia in the animal kindom, but indicates these subjects have recently been addressed by others in Croonian lectures, specfically by Professor [Santiago] Ramon y Cajal and Professor Held in Leipzig. 5 March 1908