I have not carried through the analogous investigation for stature, because in this case the increase might simply be ascribed to the better nutrition of most of the north and central European immigrants after their immigration into this country.

There is another hypothesis which might account for the observed changes of type. If it were assumed that among the descendants of immigrants born in America there are an appreciable number who are in reality children of American fathers, not of their reputed fathers, a general assimilation with the American type would occur. Socially this condition is not at all plausible, but on account of the importance of the phenomenon that we are discussing it should be considered. I do not think that any of the observations that have been made are in favor of this theory. The changes that occur in the Bohemians who arrive here as young children, the different directions of the changes in distinct types, particularly the shortening of the head of the Bohemians and of Italians, do not favor the assumption. Furthermore, if the modification were due to race mixture the similarity between fathers and American-born children should be less than the similarity between fathers and foreign-born children. There is no indication that this is the case, for the index of correlation which expresses the degree of similarity is about the same in either group, as will be seen from the following table:

TABLE 16.-Correlations between parents and children: Hebrews.

That the index of correlation is a sensitive index of similarity and, we may say, of purity of sexual relations, is shown by the correlation for color of hair between Hebrew mothers and daughters, which is exceptionally low (0.13 for 616 cases), because many mothers wear wigs, and perhaps some daughters dye their hair.

This hypothesis is also shown to be untenable by the comparisons of fathers and mothers with their own foreign-born and Americanborn children. These comparisons show that the differences are the same in the case of fathers and children and of mothers and children. so that obviously the same conditions must control the relations between fathers and their children and mothers and their children. In other words, the fathers must be considered as the true fathers of their children.

It seems to my mind that the changes that have been observed in the transition of Europeans to the environment of New York must

be considered as analogous to those that the European rural population undergoes when it moves from the country to the city. Ammon," who was the first to observe these changes in Baden, ascribes them to the effects of natural selection, which weeds out among the south Germans that move to the city the more short-headed type, while the long-headed type survives. Livi, who made similar observations in Italy, believed that the changes are simply due to the wider range of territory from which urban populations are drawn. The more varied descent, from which the urban population is derived, brings it about that in a region inhabited by short-headed people the urban population will be more long-headed, while in a region inhabited by long-headed people it will be more short-headed, than the rural population.

I believe that this factor is of considerable importance in the development of differences between urban and rural population; but our American observations show that there is also a direct influence at work. Ammon's observations are in accord with those on our American city-born central Europeans; Livi's, with those on our American city-born Sicilians and Neapolitans. Parallel observations made in rural districts and in various climates in America, and others made in Europe, may solve the problem whether the changes that we have observed here are only those due to the change from rural life to urban life. From this point of view the slight changes among the Scotch are also most easily intelligible, because among them there is no marked transition from one mode of life to another, most of those measured having been city dwellers and skilled tradesmen in Scotland, and continuing the same life and occupation here.

On the whole, it seems more likely that the phenomena observed in the cities of Europe and among the descendants of immigrants in America are analogous, but not the same; that both are expressions of the general plasticity of human types when living under different conditions. The variability of the Hebrew type in different parts of Europe, which has been so clearly demonstrated by Maurice Fishberg, is also in favor of this theory. Doctor Fishberg has shown that the Hebrew type in various parts of eastern Europe varies somewhat, and generally in accordance with the type of the surrounding population. He was inclined to interpret this phenomenon as due to intermixture, but it may well be an expression of the effect of environment upon the same type.

It may be possible that the wider range of intermarriages which occur in America may have an effect upon human types. The actual intermarriages in small villages in Europe are preponderantly of such character that the same strain will persist for a long period with very slight disturbance by intermixture from outside, the majority of intermarriages in small communities being generally in that community. When immigrants leave their home and settle in large cities this permanence of strain is entirely broken; and it seems at least possible that the changes which have been noticed in

a Natürliche Auslese beim Menschen, 1893. Zur Anthropologie der Badener, 1899, pp. 431 et seq. and 615 et seq.

Antropometria Militare, 1896.

c Materials for the Physical Anthropology of the Eastern European Jews (Mem. Am. Anthr. Ass., Vol. I., 1905, p. 1 et seq.).

urban types, both in Europe and in America, may in part be due to this cause. Our present views of heredity would make it plausible that a disturbance of the established type would occur in such a case, even if the two intermarrying types are not markedly distinct. It has not been possible up to this time to investigate the material thoroughly from this point of view; but I believe the theory deserves to be followed up. Modifications in the distribution of sexes have been observed in an analogous case in the Argentine Republic, where it has been shown that in intermarriages between Spaniards and Italians the proportion of the sexes changes materially. The information contained in our material will permit us to investigate the question here suggested.

Earnest advocates of the theory of selection might claim that all these changes are due to the effects of changes in death rate among foreign-born and American-born; that either abroad or here individuals of certain types are more liable to die, and that thus these changes are gradually brought about. On the whole, it seems to my mind, the burden of proof would lie entirely on those who claim such a correlation between head index, width of face, etc., and death rate-a correlation which I think is highly improbable, and which could be proposed only to sustain the theory of selection, not on account of any available facts. I grant the desirability of settling the question by actual observations, but until these are available we may point out that the very suddenness of the changes after immigration, and the absence of changes due to selection by mortality among the adult foreign-born, would require such a complicated adjustment of cause and effect in regard to the correlation of mortality and bodily form that the theory would become untenable on account of its complexity. It would be saying too much to claim that all the distinct European types become the same in America, without mixture, solely by the action of the new environment. First of all, we have investigated only the effect of one environment, and we have every reason to believe that a number of distinct types are developing in America. But we will set aside this point and discuss only our New York observations. Although the long-headed Sicilian becomes more roundheaded in New York and the round-headed Bohemian and Hebrew more long-headed, the approach to a uniform general type can not be established, because we do not know yet how long the changes continue and whether they would all lead to the same result. fess I do not consider such a result as likely, because the proof of the plasticity of types does not imply that the plasticity is unlimited. The history of the British types in America, of the Dutch in the East Indies, and of the Spaniards in South America favors the assumption of a strictly limited plasticity. Certainly our discussion should be based on this more conservative basis until an unexpectedly wide range of variability of types can be proved. It is one of the most important problems that arise out of our investigation to determine how far the instability or plasticity of types may extend.

Whatever the extent of these bodily changes may be, if we grant the correctness of our inferences in regard to the plasticity of human types, we are necessarily led to grant also a great plasticity of the mental make-up of human types. We have observed that features of the body which have almost obtained their final form at the time of birth show modifications of great importance in our new surroundings.

We have seen that others which increase during the whole period of growth, and are therefore subject to the continued effect of the new environment, are modified even among individuals who arrive here during their childhood. From these facts we must conclude that the fundamental traits of the mind, which are closely correlated with the physical condition of the body and whose development continues over many years after physical growth has ceased, are the more subject to far-reaching changes. It is true that this is a conclusion by inference; but if we have succeeded in proving changes in the form of the body, the burden of proof will rest on those who, notwithstanding those changes, continue to claim the absolute permanence of other forms and functions of the body.

PROBLEM OF HEREDITY.

In the course of our investigation it has been necessary to inquire into certain problems which have no immediate connection with the change of type of the descendants of immigrants, but which are of great importance for our knowledge of the amalgamation of different types in America. The most important of these is the problem of heredity.

Two theories of heredity are being held. In accordance with one, the children show a tendency to revert to a type intermediate between the types of the two parents-a mid-parental type-or, in cases of changes of types, to another type dependent upon the mid-parental type. In other words, the characteristics of the parents are blended in the children. According to the other theory, the laws of heredity act rather in such a way that, in regard to certain traits, either the father's or the mother's type, or the type of a more remote ancestor, is reproduced, and that certain parental traits may be dominant over others. In a generalized way we may say that by dominance is meant the tendency of one particular trait either the father's or the mother's to appear with greater frequency in the children than the corresponding but different trait of the other parent. It does not necessarily follow that all the traits of the same type are dominant, but dominant traits may be present in both parents, some in one, some in the other.

In a mixed population, like that of America, in which the frequencies of mixtures increase with the increasing social amalgamation of the descendants of immigrants, these questions are of prime importance, and it seemed desirable to obtain as much information as possible on this point.

An inquiry into the values of the cephalic index has shown clearly that the type of heredity in intermarriages in the same race is that of alternating heredity. Children do not form a blend between their parents, but revert either to one type or to the other. The method by means of which this problem has been investigated is based on the consideration that in case children show a tendency to revert to a type intermediate between that of father and mother, the variability of all the children in each family must remain the same, no matter what the difference between father and mother may be. On the other hand, if there is a reversion to the parental types, we must expect that the variability of the children in each family will increase with the difference in type between the two parents. The actual calculation of these data requires a reduction of the results

according to the number of children to each family. After this reduction was made and the cephalic index of the mother reduced to corresponding male values, the following results were obtained:

TABLE 17.-Difference in cephalic index between father and mother, and corresponding variability of children.

No evidence has been obtained showing that one type is dominant, but all show equal degrees of correlation between father and child and between mother and child and for various values of the cephalic index.

The exact character of the alternating inheritance can not be established from the data at our disposal. Although a large number of families have been investigated, they are all families consisting of father and mother belonging to the same type, and consequently cases of great differences between the parents are rare; and these are the ones which bring out the facts of alternating inheritance most clearly. It seems from the discussion of the available data that in the type of heredity investigated—that is, of the cephalic index among members of the same type of man-the facts agree best with the theory which assumes the absence of dominant traits in the type, an equal frequency of reversion to the parental types, and a lesser reversion to ancestral types; in short, an almost typical alternating type of inheritance.

PHENOMENA OF GROWTH.

It has also been found necessary to investigate the phenomena of growth. The older investigations of Bowditch, Roberts, Peckham, Porter, and myself, not to mention many later ones, have shown that there is a period of marked acceleration of growth during the period of adolescence. Our inquiries have demonstrated that a similar period of acceleration occurs in the growth of the head, most markedly in the growth of the length of the head, and that the period is synchronous in both sexes with the rapid increase in the bulk of the body. The occurrence of this period of acceleration of growth during the period of adolescence is of interest because the periods of rapid growth of different parts of the body are not by any means the same throughout. (Table 18, figure 22.)

The material for this investigation was obtained from the tables published by Röse, Ranke, Boas, and by use of the tables of the Immigration Commission.

a C. Röse, Beiträge zur europäischen Rassenkunde, Archiv für Rassen- und Gesellschafts-Biologie, Vol. II, 1905; Vol. III, 1906.

bOtto Ranke, Beiträge zur Frage des kindlichen Wachstums, Archiv für Anthropologie, N. S. Vol. III, p. 161 et seq.

c Franz Boas and Clark Wissler, Statistics of Growth (Report of the U. S. Commissioner of Education, 1904, pp. 26, 27).

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