In the manner as the material in the foregoing investigation has been dealt with, thus on the basis of the polymery theory, the terms brachycephaly and dolichocephaly have undergone some alteration. We now speak of factors for brachycephaly, resp. for dolichocephaly and understand by them factors, increasing, resp. decreasing the index with a certain amount. Thus indices contain factors both for brachycephaly and for dolichocephaly. The extremely high and the extremely low indices alone, contain factors only for brachycephaly, resp. for dolichocephaly. The terms brachycephaly and dolichocephaly, as used otherwise, thus in the sence of indices being greater, resp. smaller than 80, represent compound magnitudes: a brachycephalic index is brought about through the presence of some factors for brachycephaly. The same indices may be different compositions of factors.