5. to solve the problem of maintaining or gradually improving the intelligence level of its population will thereby benefit enormously. I should therefore like to be allowed to make a few remarks on this point by way of conclusion. The hope of exterminating the mentally defective by sterilizing them is damped by the knowledge that nine-tenths of the parents of defectives possess a degree of intelligence which is within the limits of the normal. If borderline cases are counted as defectives then the prospects, in theory, are much more hopeful, for little more than two thirds of the parents of borderline cases could then be counted as normal. But an insuperable difficulty arises in practice, for the borderline cases are very numerous indeed and they cannot be sharply distinguished from the normal. Mental ability is a graded character but sterilization is not a graded process: it is, thus, an inefficient instrument for dealing on a large scale with the problems of the eugenics of intelligence. Moreover, the appreciation of the significance of declining birth rate is stimulating people to think more carefully of the possibilities of providing positive financial and social inducements to fertile married couples. An advantage of positive measures for combating a decline in birth rate is that they can be used to adjust the differential fertility with respect to intelligence. Unlike sterilization, which is an all or nothing process, encouragement can be graded, as in some of the proposed schemes of family allowances. If men and women capable of skilled and professional work could be persuaded to marry young and to risk having large families, the educational outlook for the future would be very much improved. Closely associated with the financial aspects of small and large families are the social aspects. If rural life could be made attractive, [insert]enough to prevent migration [strikeout] of the intelligent to the towns[end insert], without allowing its traditions to be forfeited, a better balanced population would be obtained. We sometimes are told that the social services tend to diminish fertility. Thus, if the amenities of life and education level of the "submerged tenth" of the population in industrial areas could be raised, the fertility in this group would probably tend to grow less. In expressing the view that the average level of intelligence in this country is likely to diminish if conditions remain as they are at present, I have excluded from the discussion the question of the genetics of mental derangement: this I consider to be a separate problem. At the same time, I do not wish to convey the impression of believing intelligence to be the only desirable mental character: mental health and adjustment to society are at least as important. Antisocial tendencies and delinquency may be more frequent in those of defective intellect than in the normal, but these traits are more dangerous in those of high mental capacity. Mental hygiene is just as necessary in an intelligent as in a dull community, but the prospects of success of treatment are favourable only in a society composed of people who have plenty of innate ability to profit by experience. References [end]