Genetic Data on Drosophila Affinis, with a Discussion of the Relationships in the Subgenus Sophophora.

ROSOPHILA af inis Sturtevant is a member of the subgenus Sophophora (STURTEVANT 1939), closely related to D. athabasca, azteca, algonquin, narragansett, and Seminole (STURTEVANT and DOBZHANSKY 1936b). Cytologically, all the members of this group (Seminole has not been examined) are aberrant in the subgenus in that they have-in addition to a large V-shaped X chromosome and a small dot-like autosome-three twoarmed autosomes (V-shaped or J-shaped-see figure I). The short arm of one of the J’s appears to be wholly heterochromatic, but there remain five autosomal euchromatic arms in addition to the dot-that is, including X and the dot, a total of eight. This was shown by MILLER 1939, for algonquin; for azteca and athabasca this conclusion rests on unpublished information communicated by PROF. T. DOBZHANSKY and MR. E. NOVITSKI. In most other members of the subgenus (melanogaster, pseudoobscura, subobscura, etc.), the total number of euchromatic arms is six. As indicated later in this paper, the European obscura probably agrees with the afinis group, ananassae has an extra X-arm, and in willistoni, earlei, and their relatives the dot has disappeared. The study of mutant genes in afinis was undertaken in order to throw some light on the relation between the distribution of genes in the ufinis configuration and that in the other members of the subgenus.