ABSTRACT
The possibility of using inherited abnormalities in place of conventional experimental embryological methods has been explored by several workers in Drosophila, where there is a large range of lethal and female sterile genes readily available (reviewed Waddington, 1956). These genes are usually pleiotropic, i.e. with manifold effects, and tracing these diverse effects back as far as possible to a single primary defect gives information about the corresponding developmental mechanisms in the normal embryo. Two disadvantages have attended these studies: (1) dipteran embryology is extremely specialized and difficult to relate to that of other insects, (2) it is almost entirely mosaic in character, and therefore throws no light on the important subject of tissue interactions.
