X.—Spermatogenesis inDrosophila obscuraFallen. I. The Cytological Basis of Suppression of Crossing-over

Abstract

During recent years it has become increasingly possible to interpret unusual genetic phenomena by reference to peculiarities in chromosome behaviour. Examples of such cytological explanation are found in the studies of triploidy by Bridges and Anderson (1924) and Redfield (1930, 1932), and of translocations by Dobzhansky and Sturtevant (1930), Rhoades (1931), and Dobzhansky (1932a). But, thus far, the phenomenon of complete linkage in the male of Drosophila has not been explained satisfactorily by direct observation of spermatogenesis. Doubtless this has been due partly to technical difficulties, and partly to the fact that chromosome behaviour is only now beginning to be understood. However, the first difficulties have been eliminated by Metz (1926), Guyenot and Naville (1929), and Huettner (1930); and the second by Belar (1928), and more recently by Darlington (1932b).