Mutant larvae show greatly delayed larval growth. Embryos derived from females carrying homozygous germline clones show defective cuticles indicative of an early requirement for sun+ activity. Nuclear migrations during cycles 4-10 appear normal, and early cortical divisions (nuclear cycles 10 and 11) are indistinguishable from wild type. However, the mutant embryos have highly irregular nuclear spacing during the late cortical divisions. There is an increasing tendency of the nuclei to cluster, coincident with the occurrence of nuclear fusion, which is rarely seen in wild-type embryos.