The Genetic Structure of American Populations of Drosophila Melanogaster

When brought to Amherst, the cultures contained between them some 25 old appearing flies and many larvae. The larvae need not have been the offspring of the flies which were found in the bottles, since there was nothing to prevent other flies from entering and leaving during the period of exposure. In the laboratory, the old flies and about 2 0 0 of the F1 from the four cultures were put together in a large culture bottle. A random sample was taken from their sons for analysis. This sample consisted of F1 and F 2 of native Belfast flies. Analysis through the test generation was carried out by PLOUGH. The data appear in the tables as Maine 38. The Maine 38 stock was kept in unselected mass cultures of about IOO pairs of parents for each generation. A random sample of flies was taken from the stock bottle in March of 1942, about 60 generations after the stock was established. It was analyzed by a student, MR. R. SEWARD, under the author's supervision. This second sample appears in the data as Maine 42.