Equally difficult to understand is the spread of morphological traits from one language to another. Nevertheless, I am very much inclined to believe that such transfers do occur, and I even consider it possible that they may modify fundamental structural characteristics. An example of this kind is the intrusion of nominal cases into the upper Chinook dialects, presumably due to Sahaptin influence. I believe that the peculiar development of the second third person in Kutenai, which is so characteristic of Algonquin, is also due to a contact phenomenon, because we find hardly anywhere else a similar development of this tendency. Still another case of peculiar parallelism is found among the Eskimo and Chukchi. Notwithstanding the fundamental differences between the two languages, the modern development of the verb with its numerous semi-participial forms, shows a peculiar parallelism. The traits in question are entirely absent in neighboring languages, and for this reason it is difficult to abstain from the conclusion that these similarities must be due to historical reasons.
The distribution of these phenomena the world over is so irregular, that it would be entirely unwarranted to claim, that all similarities of phonetics, classification of concepts, or of morphology, must be due to borrowing. On the contrary, their distribution shows that they must be considered as due to psychological causes such as the unavoidable necessity of classification of experience in speech, which can lead to a limited number of categories only, or the physiological possibilities of articulation, that also limit the range of possible sounds which are sufficiently distinct to the ear for clear understanding.
To give a few examples: it would hardly be possible to claim that the numerous instrumental prefixes of the Haida and those of Shoshoni, Kutenai, and Sioux, are historically related. It is true that Shoshoni, Kutenai, and Sioux form a continuous group to which might be added many of the Californian languages. Considering the continuity of this area and the absence of analogous forms outside, I am strongly inclined to believe that some historical reason must have led to their peculiar development, but it would be difficult to connect historically the Haida with this district.
