ANTHROPOLOGY: F. BOAS 
715 
tion and acceleration of growth may also account for varying propor- 
tions of the limbs. On the other hand, we have no information what- 
ever that would allow us to determine the cause of the physiological 
diminution in the size of the face that has been observed in America, 
nor for the change in the head-index that occurs among the descendants 
of immigrants. 
Furthermore, there is nothing to indicate that these changes are in 
any sense genetic changes; that is to say, that they influence the heredi- 
tary constitution of the germ. It may very well be that the same 
people, if carried back to their old environment, would revert to their 
former physiological types. 
In fact, it can be shown that certain features are strictly hereditary, 
and that, although the physiological form of a genetic type may vary, 
nevertheless the genetic type as such will exert its influence. Professor 
von Luschan has repeatedly called attention to this fact as reveaJed 
in the modern populations of Asia Minor, where, notwithstanding the 
mixture which has continued for at least four thousand years, the char- 
acteristic Armenian, Northwest European, and Mediterranean types 
survive in the mixed population. Similar examples may be observed in 
Italy. I have calculated the variabiHty of the head-form that is found 
in different parts of Italy, based on the data collected by Ridolfo Livi. 
The head-form of the North Itahans is excessively short. The head- 
form of the South Italians is decidedly elongated. In between we. 
find intermediate forms. In the Apennines, we have, in addition to 
the mixture of these two Italian forms, a marked immigration from the 
Balkan Peninsula, which introduced another short-headed type. As 
a result of these long-continued mixtures, we observe low degrees of 
variability in northern and southern Italy, high degrees of variabiHty 
in the central regions, particularly in the Abruzzi. These indicate 
permanence of the component types of the mixed population. 
During the last few years some new data have been collected that 
confirm my previous observations. I have pointed out several times 
that changes of types have been observed in Europe wherever a care- 
ful comparison between city population and country population has 
been made. Generally the changes that occur there have been ascribed 
to selective influences; but the intensity of selection would have to be 
so great, that it does not seem plausible that they can be explained by 
this cause. 
In conjunction with Miss Helene M. Boas, I have made a comparison 
between the head-forms of the city populations of Italy and of the 
rural population in the areas surrounding the cities, and compared 
