106 



Shull 



The F3 families of the second group, as arranged in Table II, 

 iuclude those which are referable to the expected ratio 15 : 1, the parents 

 of these families having had both the duplicate genes, C and D, 

 heterozygous. As tliis was the condition of all the Fs families from 

 which the F3 was derived, the F4 families produced l)y bursa-pastoris 

 indinduals in tliis group should repeat the conditions found in the F3, 

 being again distributed among the same three types. Table III includes 

 27 F4 families derived from this 15 : 1 group of the F3, and 50 F5 

 families produced from the corresponding group in F4. No confusion 

 results from tabulating the two generations together in this way, as the 

 expectation is the same in both. If for any reason it should be desired 

 to distinguish between the Fj and F5 families, this may be easily 

 accomplished by reference to the pedigree-numbers. 



