Add to ORKGStudents of genetics have often been challenged to state the bearing of their work on the old controversy about the origin of species. If the challenge has often been allowed to go un- answered, it is not because geneticists failed to have an inkling that their results might, in the end, have a significant bearing on this question, but rather because they recognized the need of first putting their house in order. The futility of attempting to arrive at any reliable conclusion concerning the origin of new types until something more was known about heredity had become only too manifest during the debates of the latter half of the last century. It required no subtlety on the part of geneticists to see that only those characters can take part i...