The Morphology and Morphogenesis of the Buccal Organelles in Paramecium with Particular Reference to their Systematic Significance*

SUMMARY. A comparative cytological study of the buccal organelles in seven species of Paramecium and a critical analysis of their morphogenesis during binary fission are presented. The. results show several heretofore overlooked features of the buccal system which may possess considerable systematic significance. On the basis of the morphology of the buccal apparatus and its mode of stomatogenesis, the genus Paramecium, traditionally placed among the trichostomes, is considered to be a true member of the order Hymenostomatida. The taxonomic utility of the buccal organelles and their phylogenetic implications are discussed in the light of the fundamental principles underlying the “new systematics” of ciliated protozoa.