Every aspect of the phenotype of the daughterless (2-41.5) maternal effect mutation was found to be strongly temperature sensitive. Above 22 degrees, da/da mothers produced no daughters; however female progeny did survive the da maternal effect if the last 60 hours of oogenesis and the first three hours of embryonic development took place at 18 degrees. The females which survived under these conditions displayed morphological abnormalities in a variety of adult cuticular structures, characterisitc of cell death during development. In contrast, their male siblings were morphologically normal. Upon prolonged exposure to 29 degrees, da/da females became sterile but continued to lay eggs. Some sexually mosaic progeny from da/da mothers survived even at 25 degrees, but the distribution and development of the female tissue in these mosaics were abnormal. It is suggested that there are multiple functions of the da+ gene during oogenesis, one of which may be required specifically for the subsequent survival of female cells throughout the embryo. In addition to and distinct from its effect during oogenesis, the da mutation acted in both sexes of progeny as a recessive temperature-sensitive lethal mutation with a TSP during the first half of embryonic development.