must be held in abeyance until we can prove that these languages go back to a single stock and that they have not originated, to a large extent, by the process of acculturation.
From this point of view I should not be inclined to claim, for instance, that Tlingit and Athapascan are members of the same linguistic family. There is not the slightest doubt that the morphology of the two groups shows the most far-reaching similarities. Since, furthermore, the two languages are contiguous, the inference is inevitable that these similarities must be due to historical causes. It is, however, another question whether we are to infer immediately that these differences are due to the fact that in very early times the two groups had a common “Ursprache.” The vocabularies of Tlingit and Athapascan are fundamentally distinct, and it does not seem to me that Dr. Sapir has proved his case of relationship between the two languages by the comparison of a limited number of words that show slight phonetic similarities. The question would remain to be answered, why there should be such fundamental dissimilarities between by far the larger number of words, and the question should still be asked how these dissimilarities are to be explained.
It is true enough that in a comparison of modern Indo-European languages, without any knowledge of their previous history, it might be very difficult to prove relationship let us say, between Armenian and English and we might be compelled to adopt a similar conclusion as the one suggested here. Partially this inference would be correct, because our modern Indo-European languages contain much material that is not Indo-European by origin. The fundamental question is whether this material may become so extensive and influence the morphology so deeply that the inclusion of a language in one group or another might become arbitrary. I think it is well worth considering whether the similarities between Finnish and Indo-European, to which Sweet has called attention, may not be due to such a process of acculturation.
To sum up, it seems to my mind that a critical attitude towards our problem makes it necessary to approach our task from three points of view. Firstly, we must study the differentiation of dialects
