260 THE INDUCTIONS OF BIOLOGY. 



" John L has a son who is normal, and a daughter 



Jane, who was born with six fingers on each hand and six toes 

 on each foot. The sixth, fingers were removed. The sixth 

 toes are not wrapped with the fifth as in her father's case, 

 but are distinct from them. The son has a son and daughter, 

 who, like himself, are normal. 



" In this, the most interesting sub-branch of the descent, 

 we see digital increase, which appeared in the first generation 

 on one limb, appearing in the second on two limbs, the 

 hands ; in the third on three limbs, the hands and one foot ; 

 in the fourth on all the four limbs. There is as yet no fifth 

 generation in uninterrupted transmission of the variety. 

 The variety does not yet occur in any number of the fifth 

 generation of Esther's descendants, which consists, as yet, 

 only of three boys and one girl, whose parents were normal, 

 and of two boys and two girls, whose grandparents were 

 normal. It is not known whether in the case of the great- 

 great-grandmother, Esther P , the variety was original 



or inherited."* 



§ 86. Where there is great uniformity among the mem- 

 bers of a species, the divergences of offspring from the 

 average type, are usually small ; but where, among the 

 members of a species, considerable nnlikenesses have once 

 been established, unlikenesses among the offspring are fre- 

 quent and great. Wild plants growing in their natural 

 habitats, are uniform over large areas, and maintain from 

 generation to generation like structures ; but when cultiva- 

 tion has caused appreciable differences among the members 

 }f any species of plant, extensive and numerous deviations 

 are apt to arise. Similarly, between wild and domesticated 



* This remarkable case appears to militate against the conclusion, drawn some 

 few pages back, that the increase of a peculiarity by coincidence of " spontaneous 

 variations " in successive generations, is very improbable ; and that the special 

 superiorities of musical composers cannot have thus arisen. The reply is, that 

 the extreme frequency of the occurrence among so narrow a class as that of 

 musical composers, forbids the interpretation .bus suggested. 



