MENDEL'S LAW OF HEEEDITY 



fur is recessive in crosses with normal short 

 hair. All the immediate offspring of such a 

 cross are short-haired, but in the next genera- 

 tion long hair reappears in approximately one 

 fourth of the offspring. 



In cattle, the polled or hornless condition is 

 dominant over the normal horned condition; 

 in man, two-jointed fingers and toes (Figs. 19 

 and 20) are dominant over normal three- jointed 

 ones. This is clear from an interesting pedi- 

 gree given by Farabee of the inheritance of 

 the abnormality in a Pennsylvania family (see 

 Fig. 21). In no case was an abnormal mem- 

 ber of the family known to have married any 

 but an unrelated normal individual. It will 

 be seen that approximately half the offspring 

 throughout the four generations of offspring 

 shown in the table were of the abnormal sort, 

 — short-bodied and with short fingers and toes. 



In each of the cases thus far considered a 

 single unit-character is concerned. Crosses in 

 such cases involve no necessary change in the 

 race, but only the continuance within it of two 

 sharply alternative conditions. But the result 

 is quite different when parents are crossed 



39 



