THE GENETICS OF TUMOR TRANSPLANTATION 285 



Table 5 



The Growth of Tumors dBrB and dBrA in Two Strains of Mice and 



IN THE Progeny of Crosses between These Strains 



Anah'sis of the simultaneous reaction of the animals to the two tumors 

 indicated that two of the three genes that were involved in the case of the 

 tumor dBrA are the same as those which are active in the case of dBrB. 

 The two thus bear the following relation to one another. 



Table 6 

 Expected and Observed Percentage Takes of Tumors dBrB and dBrA 



Tumor dBrA needs genes A, B and C. 

 Tumor dBrB needs genes A, B. 



These experiments helped to strengthen the probability that the working 

 hypothesis based on Little's earlier theor}^ was correct. 



