Morphogenesis and Polymorphism in Gastrostyla steinii

Clonal cultures of the hypotrich protozoan, Gastrostyla steinii, were protargol stained and examined by light microscopy. Morphogenetic stages were noted, as well as variations in the number and distribution of the frontal-ventral-transverse cirri. These cirri, for the purpose of this study only, were delineated into special topographical groups—frontal, medial, and anal. Analyses were made to evaluate possible relationships as to the number of cirri between these groups and for the total number of cirri of the organisms, and, finally, to show likely relationships between morphogenetic events and patterns of cortical variation. An interesting “extra marginal row phenomenon” also was noted and shown to have variations of its own. Cirral polymorphism is presumed to be under genic control with the ultimate individual corticotype under the influence of an underlying gradient. A “stability profile” for the organism and for each cirral group was erected and discussed with emphasis on a gradient mechanism.