Observations on the Fine Structure of Dictyocha Fibula Ehrenberg. I. The Skeleton¹

SUMMARY Carbon replicas of the skeletons of a cultured clone of Dictyocha fibula reveal a surface pattern of bands 4–5 nm wide. Reticular ornamentation previously reported for fossil skeletons is not present. Skeleton formation may proceed from an initial series of dichotomous outgrowths of an elongate, formative vacuole; which later fuse at junctures of the basal ring and supporting bars. The presence or absence of an apical ring may be a function of variation in the duration of the synthetic stage of predivision among individuals within the same clone.