Although one of the important objects of a mental deficiency colony is the return of patients to the general population, the number of cases on licence, or discharged from the provisions of the Mental Deficiency Acts, is not an accurate indication of the improvement-rate. Cases proceed on licence because their behaviour is sufficiently satisfactory for the houses to which they go. A defective may show no change whilst in the colony, but the environment to which he goes may be better than that which he left before entering the colony. Alternatively, the defective may return to the same home circumstances which he left, but he may have improved. All gradations of combinations of change of environment or of defectives occur.