One of the most dramatic features in the history of Indo-Aryan languages has been the utter collapse of the ancient prefixal system which had been used for expressing the various shades of human concepts. The dramatic nature of this break-down will be particularly appreciated when we take into account the fact that even for an ordinary concept such as ‘to come’, Sanskrit had to depend upon a prefix, viz. ā ‘hither’, so that ‘to come’ was indicated by ā-gam- or ā-yā, literally ‘hither—move’. This implies that the roots gam- or yā- by themselves denoted movement in general and during the formative period of Sanskrit a stage is conceivable when going and coming were linguistically undifferentiated. This supposition may perhaps be somewhat confirmed by a parallel occurring in two languages at the present day, viz.