In 1922, 1·3 per cent. of the school-age population of London was mentally defective. Delinquents show a slightly greater average intelligence than the mass of day special school children in the (M.D.) schools. In adults the average mental age of defectives is 7·9 and of defective delinquents 8·5. In a percentage frequency of different offences, wandering provided the maximum number of cases showing a low grade of mentality. Shurbsall agrees with East's observation that women charged with soliciting show a relatively high mental age for defectives. In men, stealing is more frequently found among the unemployable classes, while, in women, the largest figure is for those in regular work. The author thinks that Burt's definition of temperamental defectives rather than moral imbeciles, would only include the unstable emotional temperament. In