Cleavage Patterns in Drosophila and Mosaic Formation

The study of the early developmental history of Drosophila melanogaster from the fertilization of the egg to the end of gastrulation, has been undertaken in the hopes of obtaining more definite information regarding the cleavage pattern of the egg and the distribution of the cleaving nuclei to the forming blastoderm. In the later stages, special attention has been given to those phases of the developing organism which produce external structures of significance to the geneticist. More specifically, the endeavor has been made to lay an embryological foundation which might serve as a means of interpreting the conditions found in various types of gynandromorphs and mosaics. While the earlier literature concerning dipteran development is replete with different phases of embryological investigations of various flies, it is doubtful whether a complete embryological history of the entire dipteran embryo has been written. In order to trace the ultimate fate of the descendants of the nuclei, it is necessary to have an exact understanding of the development of the particular generic group to which the fly belongs.