Spontaneous Mutability in Drosophila

When Muller in 1927 first clearly demonstrated that mutations could be induced by X-radiation, I think it was generally believed that the discovery would be most useful in testing evolutionary theories, or as a practical method for producing particular desired mutations, rather than as a precise tool for the analysis of the nature of the gene. Yet in the intervening fifteen year period chiefly as a result of the use of radiation techniques, there has emerged a new and chemically more satisfactory picture of the gene than was held in earlier days. Though the details have been by no means filled in, nevertheless the older crude model of a row of beads attached to a chemically unrelated strand, has now been replaced with a concept which visualizes the genes as definitely placed entities, loosely combined at intervals with an intervening fibrous protein. This refining process, together with the present confusion