Summary 1. The development of two species, Secotium erythrocephalum Tul. and S. novae-zelandiae G. H. Cunn., is dealt with. 2. Differentiation of the stipe and columella precedes the formation of the first glebal cavity in S. novae-zelandiae, and follows its appearance in S. erythrocephalum. 3. Following the appearance of the first glebal cavity, the gleba of both species becomes further differentiated through the appearance of numerous lacunae in the primordium of the gleba surrounding the columella. 4. Spores make their appearance shortly after the formation of the first few cavities, when the plant is less than one-third the normal size. 5. A definite partial veil is present, but a universal veil is wanting. 6. Early developmental stages, until the appearance of the first glebal cavity resemble those of Agaricus, later stages resemble certain genera of the Hymenogastraceae. 7. Spores and hyphae are binucleate. 8. The genus should be retained in the Gasteromycetes, preferably in a distinct family, the Secotiaceae (emended).