Wing Vein Development in Crossveinless-like Strains of Drosophila Melanogaster.

HE analysis of adult phenotypic differences resulting from experimental or genetic modification of a developing system sometimes yields a useful description of the course of development in that system. Such a description may include, explicitly or not, the ontogenies of the ultimate character differences; therefore, it is desirable that the basic information should include the morphological facts of those ontogenies. At issue here is not only the possibility that the causes of the development may be recognized in preadult structure, but as well the requirement that the structure assumed in theory must be kept consistent with the structure in fact. This paper provides part of the morphological information, in anticipation of any possible speculation, for a phenogenetic analysis of polygenic crossveinless-like (cvl) strains of Drosophila melanogaster. The general information of Drosophila wing development is already provided in detail by AUERBACH (1936) and by WADDINGTON (1940). This has been summarized by BODENSTEIN ( 1950), whose own observations were in essential agreement. The present study is restricted to that part of the total development in which the wing veins are becoming manifest, and further limited by an emphasis upon the formation of the posterior crossvein and its associated longitudinal veins. Within these confinements we not only can confirm that part of the earlier description of normal development, but we recognize new variant patterns of wing vein formation among genetically different strains of crossveinless type. Consideration of these facts will aid in understanding of the epigenetics of Drosophila crossvein determination.