Development of the Tracheal System in Drosophila melanog-sterThe development of the tracheal system of Drosphila melanooaster is being traced by examining the impact of pattern disrupting mutations upon the normal development of the tracheal tree. The procedure depends upon a tissue specific P-element which carries the B-galactosidase producing gene, lac Z. Visualization of the tracheal system is attained through immunohistochemical staining of the embryos. The P-element, which is present in the sma strain of Drosophila melanogaster, is incorporated into the genome of flies that have pattern disrupting mutations. The resulting defects present in the tracheal system will be used to develop a sequence of gene activation and assist in the formation of a scheme of the development of the tracheal system in Drosophila, melanogaster.