Abstract:
Drosophila, melanogaster, commonly known as the fruit or vinegar fly, has been used in various biological experiments since 1905 when Carpenter studied its reactions to light, to gravity, and to agitation. In 1906 Castle, Carpenter, Clark, Mast and Burrows published the results of their investigations on the effect of inbreeding. Their work showed that there is no decrease in the fertility of an individual as a result of close inbreeding. In 1907 Lutz reported that the result of some observations on the inheritance of a wing-vein modification. In 1910-11 a paper by Delcourt and Guyenet appeared which dealt with the effect of food conditions on Drosophila. The question of the effect of inbreeding on fertility was also studied by Moenkhaus. He also made observations on the variations of the sex-ratio in relation to selection. This work was published in 1911. The work then, up to this time, had practically all been of a non-genetical nature for the value of D. melanogaster for genetic work had not as yet been realized. However, with the appearance of the first mutant the work took a new turn, for this species has proved to be of inestimable value in the field of genetics. Firstly, it thrives under laboratory conditions; secondly, its short life cycle makes it possible to raise many generations in a comparatively short period of time; thirdly, the chromosome number is very small, and, lastly, the form has given rise to many mutations. Through his work with this fly, Dr. Morgan has brought the chromosome theory of heredity to its present stage. The flies were raised on banana-agar culture at ordinary room temperature. They were removed from the mating bottles three or four days before the new flies were expected to hatch and no flies were counted after the tenth day from hatching, since ten days is the length of the normal life cycle. In this way the possibility of including flies of a succeeding generation was obviated....
