1. Selfing in Paramecium aurelia, syngen 5: persistent instability of mating type expression;Bleyman;J. Exp. Zool.,1967
2. Protozoology
3. Experimentelle Untersuchungen an Euplotes crassus. I. Paarungssystem, Konjugation and Determination der Paarungstypen;Heckmann;Z. Verbungsl.,1964
4. Age-dependent intraclonal conjugation in Euplotes crassus;Heckmann;J. Exp. Zool.,1967