116 The Eugenics Review to biological problems, comparable to the researches upon which a mathematical physicist can draw in the solution of special difficulties." One important caution must be added. In the course of evolution there have certainly been sudden changes, for example changes of chromosome number, and in all probability the formation of new species by hybridization. Dr. Fisher's theory takes little or no account of these, and for this reason cannot be regarded as a full account of evolution by natural selection. The last five chapters will be of most interest to readers of this journal. The attempt is made to explain the fact that all civilizations previous to our own have decayed. Very strong evidence is brought forward that the main cause of changes in the composition of human populations is the difference in effective fertility between different genotypes. It is further argued that the most important heritable causes of such difference are differences of moral temperament. Hence selection has tended in the past to eliminate the type of human character which favoured infanticide and abortion. The variation of fertility in relation to social class is examined, though we miss any reference to the very remarkable and perhaps significant state of affairs in Stockholm, where the poor are breeding no faster than the rich. So far most members of the Eugenics Society will be in agreement with Dr. Fisher. His last two chapters are likely to raise a good deal of opposition. He regards the social promotion of infertility as the main cause of the differential birth rate. The argument, which is at times rather subtle, is essentially a development of Galton's demonstration that marriage with heiresses, who are rich owing to the infertility of their parents, is a potent cause of the extinction of families. His suggested remedy for the dysgenic character of civilized societies is a very thorough-going system of family allowances on such a scale that infertility would no longer be a cause of social promotion. The reviewer considers that he has made out an extremely strong case. Indeed, if his biological facts are correct, it is probable that a socialistic state in which no wealth was inherited would be more eugenic than our present society, and it is a little difficult to see why Dr. Fisher's economic views are not even more radical. It is clear that Dr. Fisher's opinions are opposed to those of many believers in eugenics. The immediate effects of such a system as he proposes would probably be to increase the fertility of some sections of the poorer classes, for, as he himself admits, it would be extremely difficult to apply it to the small but, on the whole, intelligent section of the population which is not in receipt of fixed wages or salaries, but rewarded by fees from many different sources. Hence the first result of such a system might be the opposite of eugenic. The following criticisms of Fisher's social theory, among others, might be made. If the number of genes concerned in human intellectual ability is very large, the conditions in the bulk of the population are more important than those in the most intelligent and unintelligent groups. If, however, high intelligence on the one hand, and mental defect on the other, are due to rather few genes, as seems very possible, the eugenist may be justified in viewing those section of the population in which those genes are concentrated with what would otherwise be an exaggerated interest. Again, the arguments regarding the selection of moral dispositions will be rather weak until we know more about what is actually inherited. Dr. Fisher writes as if fanaticism were inherited as such. It seems more likely that the innate basis of fanaticism is a special type of suggestibility which may show itself as fanaticism in certain environments. Among the well-to-do classes to-day there is a great deal of rather unintelligent Malthusian propaganda. In fact there is something of a taboo against large families. Hence a large number of the parents of large families are people who, just because they think for themselves and react against mass suggestion, have not been affected by this propaganda. People of the [end]