130 EVOLUTION 



and dwarfs iq fog ft - t \ proportion Thus the 

 Fft generation, resulting from the self-fertili- 

 zation of the cross-bred forms or hybrids (F 1 ) 9 

 consisted pf ft.5 



The results may be expressed in a scheme: 



Parental generation Tall variety Dwarf variety 



First filial (hybrid) all the offspring tall; self- 



generation (F^ fertilized they yielded 



Second filial (inbred) 25% Tails 50% Tails 25% Dwarfs 



generation (Fj) (pure dominants) (impure dominants) (pure recessives) 



25% 50% 25% 

 Tails Tails Tails Dwarfs Dwarfs 

 (pure) (impure) (pure) 



Or, using D for the forms with the domi- 

 nant character, R for the forms with the re- 

 cessive character, and D(R) for forms with 

 the dominant character expressed and the 

 recessive character latent, the facts may be 

 expressed in a more generalized way thus 

 (after Punnett) : 



Parents "73 ^' D R 



\/ 

 First filial generation (Fj) D(R) 



ID + 2D(R) + 1R 

 Second filial generation (F 2 ) (pure (impure (pure 



dominants) dominants) recessives) 



Third filial generation (F 8 ) D ID + 2D(R) + 1R R 



Let us take as an illustration from among 

 animals, one lately well illustrated in the 



