156 THE POPULAR SCIENCE MONTHLY. 



The first fact is that this six-fingered hlacksmith will be 

 likely to transmit his peculiarity to some of his children ; and 

 some of these, again, to theirs. It is proved that, even in the 

 absence of a like peculiarity in the other parent, this strange 

 variation of structure (which we must ascribe to some fortuitous 

 combination of causes) is often inherited for more than one 

 generation. Now the causes which produce this persistent six- 

 fingeredness are unquestionably causes which " operate through 

 inheritance." The Duke of Argyll says that " natural selection 

 includes and covers all the causes which can possibly operate 

 through inheritance." How does it cover the causes which oper- 

 ate here ? Natural selection never comes into play at all. 

 There is no fostering of this peculiarity, since it does not help in 

 the struggle for existence ; and there is no reason to suppose it 

 is such a hindrance in the struggle that those who have it dis- 

 appear in consequence. It simply gets cancelled in the course 

 of generations by the adverse influences of other stocks. 



While biologists admit, or rather assert, that the peculiarity 

 in the blacksmith's arm which was born with him is transmissi- 

 ble, they deny, or rather do not admit, that the other peculiari- 

 ties of his arm, induced by daily labor — its large muscles and 

 strengthened bones — are transmissible. They say that there is 

 no proof. The Duke of Argyll thinks that the inheritance of 

 organs enfeebled by disuse is " not generally disputed " ; and he 

 thinks there is clear proof that the converse change — increase of 

 size consequent on use — is also inherited. But biologists dispute 

 both of these alleged kinds of inheritance. If proof of this is 

 wanted, it will be found in the proceedings at the last meeting 

 of the British Association, in a paper entitled " Are Acquired 

 Characters Hereditary ? " by Professor Ray Lankester, and in 

 the discussion raised by that paper. Had this form of inherit- 

 ance been, as the Duke of Argyll says, " not generally disputed," 

 I should not have written the first of the two articles he criticises. 



But supposing it proved, as it may hereafter be, that such a 

 functionally-produced change of structure as the blacksmith's 

 arm shows us is transmissible, the persistent inheritance is again 

 of a kind with which natural selection has nothing to do. If 

 the greatly-strengthened arm enabled the blacksmith and his 

 descendants, having like strengthened arms, to carry on the bat- 

 tle of life in a much more successful way than it was carried on 

 by other men, survival of the fittest would ensure the mainte- 

 nance and increase in this trait in successive generations. But 

 the skill of the carpenter enables him to earn quite as much as 

 his stronger neighbor. By the various arts he has been taught, 

 the plumber gets as large a weekly wage. The small shopkeeper 

 by his foresight in buying and prudence in selling, the village 



