180 Inheritance of Acquired Characters 



any argument against the inheritance of .acquired char- 

 acters. The continuous electric current for example can 

 be produced by a battery as well as by a dynamo; and 

 the fact that one can always explain it as having been pro- 

 duced by a battery does not prevent it from being actually 

 produced by a dynamo in many cases. 



This being so, let us now examine as succinctly and 

 objectively as we can each of the four arguments : 



1. No value can be attributed to the fact of the 

 exercise of a function only a single time during life. 

 In the first place, it is possible that it may formerly have 

 been exercised repeatedly by the ancestors of individuals 

 now living. In the second place this singleness does 

 not exclude in any way its inheritance as a habit acquired 

 by exercise. For the fact of having performed a given 

 function even though only a single time, would certainly 

 leave in the parent organism a potential disposition to 

 perform it again and with greater facility in similar 

 physiological and external circumstances; therefore 

 the conception that this disposition and this greater 

 facility would be represented in descendent organisms 

 represents only an ordinary case of inheritance. 



2. As for the second argument one cannot but 

 recognize that for certain formations the statement of 

 Weismann that they can be due only to natural selection 

 seems very probably true. 



But it must be remarked that to support his assertion 

 Weismann attributes a merely passive function to many 

 parts in which it is very questionable. 



Why for instance should we not regard the carapace 

 of the turtle as a true and functional adaptation due to 

 the stimulus of the environment to which the skin of 

 the animal had reacted by a secretion constantly richer 



