Referee's report by Charles James Martin, on a paper 'Nitrification of sewage' by George Reid Sectional Committee: Physiology Recommended for publication in the 'Proceedings of the Royal Society of London'. Results have valuable practical application. Suggests possible omissions, to make the paper shorter and more suitable for the Proceedings. Reference should be made to the work of Harriette Chick ['A study of the process of nitrification with reference to the purification of sewage', DOI: 10.1098/rspb.1906.0015 Vol.77 1906]. [Published in the 'Proceedings of the Royal Society of London'] Endorsed on verso as received 12 July 1906. 11 July 1906