The localization of alkaline phosphatase during the post-embryonic development of Drosophila melanogaster.

IN the previous communication (Yao, 1949ft), alkaline phosphatase has been shown to be in some way connected with histo-differentiation during Drosophila embryogenesis. The post-embryonic development of Drosophila includes, besides a period of larval growth, the phenomenon of metamorphosis which involves the destruction of most larval organs and the simultaneous development of imaginal organs from groups of embryonic cells known as imaginal disks. It is evident from Geigy's (1931) classical experiment that the Drosophila egg, at the time of fertilization, is already endowed with both the larval and the imaginal developmental patterns. From the standpoint of developmental physiology it would appear, therefore, that embryogenesis aims at the realization of the larval pattern, and post-embryonic development at that of the imaginal pattern. Since the basic processes through which these two developmental patterns are brought into reality are fundamentally the same, one might expect an active participation of alkaline phosphatase in metamorphqsis as well as in embryogenesis. It is the purpose of the present paper to give an account of the activity of this enzyme in the larval arid pupal life of the fly.