OTHER METHODS OF SEX-DETERMINATION 215 



porous mycelia of one strain unite (i.e., give mycelia with 

 clamp connections, etc.) with all the monosporous mycelia 

 of the other strains. In Table 2 the pairing of eleven 



Table 2, 



monosporous mycelia from a fruit body from one lo- 

 cality (Edmonton, Canada) are shown to have united with 

 eleven monosporous mycelia from another locality (Win- 

 nipeg). The same results were obtained whenever strains 

 from different localities were paired. The combinations 

 carried out by Hanna gave twenty sexes for Coprinus and 

 no doubt the number could be greatly increased by ex- 

 tending the combinations to other localities. 



Not only was this cross-hybridizing carried out, but the 

 factorial hypothesis was further tested by experiments on 

 the crossed strains themselves. If the factors from the 

 different strains are treated as allelomorphic pairs, and 

 the factors in one strain are designated by Aa and Bb, 

 and those in another strain by A-a^ and B'b", there will 

 be sixteen possible hybrids formed by the union of the 



