the changes have not been so great, so that migrations appear to be one of the factors influencing births and deaths. The conclusion is that the figures fully substantiate the contention that emigration does not usually cause a permanent loss to the population, the difference between births and deaths noticeably increasing after a period of heavy emigration. The figures seem also to support the theory that the divergence between births and deaths resulting from emigration is caused, in countries with high standards of living, by a stimulation of the birth rate, and in countries of low standards by a diminution in the death rate.

Advantages and Disadvantages of Emigration. If the foregoing analysis gives the true effects of migrations on the emigrating country, the advantages or disadvantages of such migrations are easily deduced. When emigration stimulates the birth rate, a society will lose by the exchange of adults for infants, even though the new generation may be as promising as the old, for the rearing process is costly and uncertain. But if the emigrants are superior individuals the loss will be greater, for those who remain at home and become parents will be inferior and the new generation will be below the average. In 1908 Manango concluded that the physical standards of young men in Italy were decidedly lower than they had been twenty years before. It is said that in some towns few men remained who could pass the United States immigration tests. On the other hand it is conceivable that emigration might be of such a character as to improve the quality of the population. If it took the upper stratum of the lowest class, it might increase the birth rate of the more desirable middle class, although under the ordinary conditions of emigration this would not be a very probable result.

When a lowered death rate follows a period of emigration the danger is that the process of selection has been weakened, and that inferior persons are surviving, and that therefore the quality of the population is being lowered. Such a result may be much less serious in practice, however, than the theory would suggest.

1 Antonio Manango, The Effects of Emigration upon Italy; Charities and Commons, April, 1908.

a

Natural selection is not a very exact force in human society. Many children who from lack of care fail to survive the trying period of infancy might not as adults prove to be inferior. In Italy, for example, the lowered death rate has been mostly among infants; and it is entirely possible that better care, resulting either from the higher wages which would have followed emigration, or from the money sent home by emigrants, might avoid needless waste of life with nothing but good effects. If adverse selection is not of practical importance, then a decline in the death rate may be counted as an advantage to society. But if the decline is caused by the emigration of young people it still results in the exchange of young manhood and young womanhood for infancy and old age; hence the disadvantages of emigration are but little less when the improved conditions result in a lower death rate than when they result in a higher birth rate.

When emigration is followed by an improvement in the standard of living, even at the expense of a loss to the total population, it is usually advantageous, because quality in a population is more important than quantity. Improvement in the standard of living, however, does not seem to be the ordinary result of emigration. Ireland presents the sole case of a population actually declining through emigration and there the population decreased to the extent of about half the numbers emigrating. Some rise in the plane of living might take place if the rate of increase of the population were checked, even though there was no actual decrease in numbers. In some towns in Italy, since the emigration movement began, new desires have been awakened in the population, and noticeable improvements in conditions have been made, while in other towns no perceptible improvements have resulted. Improvements seem to be the result, however, of the return of emigrants and the increased wealth brought with them, rather than the effect of the lessened stress of competition in the home population. If any permanent improvement in the living conditions of a population results from emigration, it is likely to manifest itself in a lowering of the natural rate of increase. If the rate of increase returns to its old level after a few years, as is usually the case, it is doubtful

1 Antonio Manango, The Effect of Emigration upon Italy, May, 1908.

whether any extended permanent improvement has taken place in living conditions.

Conclusion. In conclusion the general effect of migrations may now be briefly summarized. It has been pointed out that the migration of a low class to a country which has passed the first stage of settlement, tends to restrict the birth rate because it increases competition, so that the immigrants add a smaller and smaller net increase to the population, till a point is reached when the loss through lowered birth rate annuls the gain through immigration and no permanent addition to the population results. When this point is reached immigration merely effects the displacement of a higher class by a lower, and it may mean also the displacement of one race by another.

Migration from a country may cause a decrease in the population and an improvement in the conditions of life, though this is not the usual result. Under the ordinary conditions of gradual emigration, a population usually merely recovers its loss, either through a rise in the birth rate or a fall in the death rate. In either case an exchange is effected of self-supporting adults for dependent infants or perhaps for persons of advanced age. And in addition to this unequal exchange, emigration may be followed by an adverse selection through the survival of the physically inferior, which results in a deterioration of the population. It may be concluded therefore that migrations, from the point of view of effect on the population, are seldom of advantage to the emigrating country; they are even more rarely of advantage to the immigrating country, and they are never at the same time of advantage to both countries.

While the immediate result of migration is a redistribution of population by diminishing the number in the emigrating country and increasing the number in the immigrating country, this is not usually the ultimate result. Such a redistribution may be permanent, however, if the migrants leave a country under conditions similar to those which existed in Ireland and go to a new country. On the other hand migrations may in the long run serve to decrease or increase aggregate populations. Migrations from Ireland to the more thickly settled parts of the United States would furnish an example of a decrease in the aggregate population, for it would diminish the population in the emigrating country and would not materially increase the population in the immigrating country. But migrations from most of the European countries to a new country would stimulate the aggregate population, for the numbers in the old country would not be materially lessened, while those in the new would be increased by practically the total number of immigrants. Finally, migrations such as take place from most of the European countries to a thickly settled country would illustrate the most peculiar phenomenon connected with great movements of populations, namely, that people may be transported from one country to another in considerable numbers without in the long run diminishing the population in the one country nor increasing it in the other.

REFERENCES FOR COLLATERAL READING BÜCHER, C., Industrial Evolution, Ch. 10. FAIRCHILD, H. P., Immigration. GOLDENWEISER, E. A., Walker's Theory of Immigration, Amer. Journ.

of Soc., 18: 342. JENKS, W., and LAUCK, W. J., The Immigration Problem. Report of the United States Immigration Commission, Vols. I and II. WALKER, F. A., Discussions in Economics and Statistics, Vol. II.

CHAPTER XXII

HEREDITY

The subject of heredity is of as much interest to sociologists as it is to biologists; and statisticians, as well as laboratory workers, have made contributions to our knowledge of the subject. Although many problems of practical as well as of theoretical interest are still unsolved, great progress has been made in the last twenty years, and some of the more important conclusions should be reviewed.

Heredity as a subject in sociology deals with those characters which the individual inherits from his ancestors and with the method of their transmission. It is therefore a subject of fundamental importance because it has to do with the characteristics of man himself and not merely with his social products.

Definitions. Before proceeding to the discussion a few technical terms should be defined. Biologists distinguish between heredity and inheritance. Castle defines heredity as “organic resemblance based on descent.” On the other hand, inheritance, in the words of Thomson, "means all that the organism is or has to start with in virtue of its hereditary relation to parents and ancestors.” A distinction is made also between inherited traits and congenital traits. Inherited traits comprise all those characters which are potentially represented in the fertilized egg cell, while congenital traits include all those present at the birth of offspring. The latter therefore is the more comprehensive term, because it includes those characters which the offspring may acquire during the period of prenatal development. Diseases, for example, are sometimes transmitted from mother to offspring during this period; but such transmission would not imply that they were inherited in the proper sense of the term. Still nother distinction to be observed is that between variations and modifications, both of which are individual peculiarities not