The Growth of the Gonads in DROSOPHILA MELANOGASTER.

As shown by DOBZHANSKY and BRIDGES (1928), triploid intersexes in Drosophila may be considered as individuals developing up to a certain moment as males and thereafter as females. The earlier or later occurrence of the turning point in the development of an intersex determines the production of an individual manifesting relatively more male or relatively more female characteristics. If the turning point occurs early in the development, intersexes are produced having more female and less male characteristics. Conversely, if the turning point occurs late, the resulting intersexes become more male-like. In the extreme cases, that is, in cases when the turning point lies very early or very late in the development, intersexes are produced which are very similar to normal females or to normal males in appearance. On the basis of these data BONNIER (1929) suggested the possibility of finding in the development of the normal females and males a phenomenon corresponding to the turning point of intersexes. The normal sexes in Drosophila differ from each other and from the intersexes by the altered balance of the female-determining and the male-determining factors. According to BRIDGES (1925), the female-determining factors are localized predominantly in the X-chromosomes, while the male-determining factors are localized mainly in the autosomes of Drosophila. Since both the Xchromosomes and the autosomes are present in the nuclei of normal females and males, both female-determining and male-determining factors are present in the germ-plasm of the normal sexual forms. Normal males may be, therefore, considered as individuals in which the turning point in