GIANTS IN LEMBADION-BULLINUM (CILIOPHORA, HYMENOSTOMATA) - GENERAL MORPHOLOGY AND INDUCING CONDITIONS

The freshwater hymenostome Lembadion bullinum exists in two forms: ''n ormal'' cells and ''giants''. The general morphology of both morphotyp es was studied, biometrical data for both morphs are presented and com pared with each other. Beside a sharp increase in cell length and widt h, giants are characterized by their larger oral region, by an increas ed number of meridional kineties, by a larger macronucleus and in cert ain stocks by the occurrence of additional micronuclei. It is shown th at the majority of giants present in a culture originates in binary fi ssion of already transformed cells. The ex novo transformation of norm al cells into giants regularly occurred in starved cultures as a conse quence of cannibalism. At higher cell densities (greater-than-or-equal -to 250 cells/ml) relatively more individuals transformed into giants than at low cell densities (less-than-or-equal-to 50 cells/ml). There is no evidence for any soluble or cell bound ''giant inducing factor'' in this species.