ANTHROPOLOGY: R BOAS 
7\7 
particularly on the outer coast of the island; while the amount of Negro 
blood in the interior is apparently not very great, except near the prin- 
cipal routes of travel. 
According to European observations, the Spanish ancestors of this 
population, while living in Spain, are long-headed. The Negro ele- 
ment is of mixed provenience, from many different parts of Africa, but, 
on the whole, the Negro in Africa is also long-headed. The West 
Indian element, judging from the few prehistoric crania that have been 
recovered, represents a very short-headed type. The modern Porto 
Rican is short-headed to such a degree that even a heavy admixture of 
Indian blood could not account for the degree of short-headedness. 
If we apply the results of known instances of intermixture to our par- 
ticular case, and assume stability of type, we find that, even if the popu- 
lation were one-half Indian and one-half Spanish and Negro, the head- 
index would be considerably lower than what we actually observe. 
There is therefore no source that would account for the present head- 
form as a genetic type; and we are compelled to assume that the form 
which we observe is due to a physiological modification that has occurred 
under the new environment. The head-form of those individuals 
whose fathers were born in Spain is noticeably more elongated than 
that of the individuals whose parents are both Porto Ricans. The head- 
index of the Mulatto population is intermediate between the index of 
the native Porto Ricans and that of those whose one parent is Spanish. 
The average index of the Porto Rican is 82.5. The average index of 
the Spaniard in Spain is less than 77. We find, therefore, an increase 
of five units here, which can in no way be accounted for by genetic 
considerations. 
I may mention in this connection that the average stature of the Porto 
Ricans is apparently almost the same as that of the Sicihans in New 
York, and that throughout the period of growth the stature follows 
about the same curve as that represented by Sicilian children living 
in America. If anything, the stature is a little lower, and there is no 
indication of that acceleration of development which is so often claimed 
to be characteristic of a tropical environment. Undoubtedly poor 
nutrition, and probably also pathological causes, have a retarding 
influence here, which might easily be overcome by better hygienic 
conditions. 
It is unfortunate that we have no accurate statistics of Porto Rican 
immigration and emigration, which would enable us to state with much 
greater definiteness what genetic type should be expected here. There 
is a popular belief in Porto Rico that in certain parts of the island, in 
