ACQUIRED AND ABNORMAL CHARACTERS. 53 



mal forms, which disqualify otherwise fine birds for 

 the show-pen. Birds are not unfrequently produced 

 which possess three back-toes, or have an extra toe 

 high up on the leg ; or, in the case of the cock, with 

 supernumerary spurs, which have been known to grow 

 in every possible direction." * 



This tendency to an increase in the development 

 of an abnormal character that has become hereditary 

 has been observed in other cases, but we are as yet 

 unable to present a satisfactory explanation of them. 

 In the case of the Dorking, the practice of breeding 

 only those birds that have the abnormal peculiarity 

 might be expected to intensify the tendency to its 

 production, by making it a dominant character ; but, 

 in the following case given by Dr. Struthers, it will 

 be safe to presume that only one parent had the ab- 

 normal character, and yet we find the same tendency 

 to its increase. " In the first generation an additional 

 digit appeared on one hand, in the second on both 

 hands, in the third three brothers had both hands, and 

 one of the brothers a foot, affected ; and in the fourth 

 generation all four limbs were affected." 2 



" In a family," says Sir H. Holland, " where the 

 father had a singular elongation of the upper eyelid, 

 seven or eight children were born with the same de- 

 formity, two or three other children having it not." 3 



Dr. Osborne reports the case of " John Murphy, 



1 Wright on "Poultry," p. 331. 



8 Quoted in Darwin's " Animals and Plants under Domestication," 

 vol. ii., p. 23. 



8 " Philosophical Transactions," 1814, p. 91 ; quoted in Darwin's 

 " Animals and Plants under Domestication," vol. ii., p. 17. 



