A Study of Intersexuality in Drosophila Virilis.

N THIS paper a detailed account of our study of intersexuality in DroI sophila virilis will be given. The progress of this work has been reported elsewhere (LEBEDEFF 1934a and b, 1938a and b). These intersexes are the result of mutative changes within the normal diploid system, and they differ from intersexes in other species genetically, morphologically and embryologically. Intersexes in Lymantria usually appear from interracial crosses, presumably due to an unbalanced condition between the female and male determining tendencies ( GOLDSCHMIDT 1934). Intersexes in Lymantria also have been reported from intraracial crosses (KOSMINSKY 1930). In D. melanogaster intersexes appear from the cross between triploid females and normal diploid males (BRIDGES 1932). The chromosomal constitution of these intersexes was found to be intermediate between that of the normal female and the normal male. Several intersexes of the same nature have been obtained from a cross between triploid D. melamguster females and normal D. simulans males (SCHULTZ and DOBZHANKSY 1933). A single autosomal gene was found to be responsible for intersexuality in D. simulans (STURTEVANT 1921). The intersexes described here are the result of the action of a single autosomal gene, called intersex (ix). The gene was called i x soon after it had been discovered, and before its nature had been studied. Since then it has been renamed ixm to denote its true nature as a gene for maleness. These intersexes were observed first in 1933 in a short vein (sv) stock which originated in 1930-31 in one of the cultures received in Cold Spring Harbor from PROFESSOR T. KOMAI, Kyoto, Japan. By inbreeding normal flies from the stock it was observed that some cultures produced intersexes in abundance, while in other cultures intersexes were less numerous. Altogether 40 cultures of the first type were obtained, these producing 2088 males, 1191 females and 962 intersexes. The number of normal males, females, and intersexes approached that of a 2 : I : I ratio; in other words, in these sets of cultures one-half of the female population became intersexual. The 41 cultures in which intersexes appeared less frequently, pro-