1. Meiotic nuclear divisions have been found in the young fructification ofMucilago spongiosa (Leyss.) Morg. var.solida (Sturg.) Lister. The first meiotic division takes place in the uncleaved protoplasm; the second in the cleaved portions, which are partly of one-spore capacity. The immature spores vary in number of nuclei; a large number did not contain a nucleus. 2. The fructifications ofMucilago have been obtained in cultures started from spores. The method of culture is described. No attempts have been made at the purification of these cultures. 3. InPhysarum didermoides (Pers.) Rost. only a single mitosis occurs in the young sporangium before the formation of the spores. The nuclei in the young sporangium are of another type than those in the plasmodium of the same species and in the fructification ofMucilago. The immature spores are uni-nucleate. 4. Mucilago appears to behave along the same line asReticularia Lycoperdon andDidymium xanthopus (ofCadman).