2s2 



BIOLOGY OF THE LABORATORY MOUSE 



Here the tumor incidence averages approximately 6 per cent. The 

 Difference is mathematically significant. 



Table i 

 dB Fi Generation (dba 9 X C57 Black cf ) 



The tumor incidence in the reciprocal F2 generations shows that the 

 difference still persists. In Table 3 are included the F2 mice descended from 



