Heredity in Protozoa 517 



nucleate strains have retained their type characteristics and have shown 

 mating reactions with other amicronucleate E. patella (37). Mating types 

 in this ciliate are correlated with the production of specific substances 

 which are released into the culture fluid and can induce conjugation in 

 certain combinations. Induction of conjugation by a given substance is 

 restricted to strains which cannot produce that substance, and may occur 

 within a clone previously showing only one mating type. For instance, 

 mating-type substance 1, from a type IV culture, induces conjugation 

 within a clone of type III, V, or VI (Chapter II). The relation of this 

 phenomenon to the results obtained in crosses of two mating types is 

 not yet clear. 



Behavior of antigenic types in conjugation 



At least four, and possibly six, antigenic types have been identified 

 within killer stock 51 of P. aurelia and its variants (82, 86). In crosses 

 between antigenic types A and B (82, 89), three different results may be 



«)•■«) 



or 



R E p R G A /N I Z \A T I O /N 



H 0( M 01 



>n c. P 5 



r\ c — E O 



O — Q 



Fig. 9. 4. Inheritance of antigenic types A (solid black) and B in con- 

 jugation of Paramecium aurelia. 



expected (Fig. 9. 4), (1) The progeny of the type A conjugant remain 

 type A and those of the other remain type B, even through autogamy. 

 (2) The type A conjugant gives rise to type A lines, while the type B 

 conjugant produces some type A, but mostly type B. (3) Descendants of 



