VARIATION AND HEREDITY 243 



its progeny, each kind of kappa controlling production of its cor- 

 responding kind of paramecin, while in serotype, two kinds of anti- 

 gen substances cannot coexist, thus being mutually exclusive. The 

 physical basis of the killer trait lies in the visible Feulgen-positive 

 kappa particles, while no such particles have so far been found in 

 association with the serotype. 



References 



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Bernheimer, A. W. and Harrison, J. A.: (1940) Antigen-anti- 

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■ (1941) Antigenic differentiation among strains of 



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