Meiosis in Dictyostelium mucoroides

THE cellular slime moulds are favourable organisms for the study of morphogenetic processes. But so far, genetic analysis of their development has been hampered by the apparent absence of a true sexual cycle, although progress has been made in parasexual genetic analysis1–3. Recent ultrastructural observations of the macrocysts of two species have suggested, but not proved, that karyogamy and meiosis are an integral part of dormancy and germination of this developmental stage4–6. We present here genetic confirmation that in D. mucoroides (strain DM-7) the assortment of mutant traits among progeny of single macrocysts is consistent only with meiosis.