84 ON HEREDITY. 



characters acquired in this way by exercise and practice can be 

 transmitted to the following 1 generations. Lamarck's theory 

 assumes that such transmission takes place, for without it no 

 accumulation or increase of the characters in question would be 

 possible, as a result of their exercise during 1 any number of successive 

 generations. 



C Against this we may urge that whenever, in the course of 

 nature, an organ becomes stronger by exercise, it must possess a 

 certain degree of importance for the life of the individual, and when 

 this is the case it becomes subject to improvement by natural 

 selection, for only those individuals which possess the organ in its 

 most perfect form will be able to reproduce them. The perfection 

 of form of an organ does not however depend upon the amount 

 of exercise undergone by it during the life of the organism, but 

 primarily and principally upon the fact that the germ from which 

 the individual arose was predisposed to produce a perfect origan. 

 The increase to which any organ can attain by exercise during a 

 single life is bounded by certain limits, which are themselves fixed 

 by the primary tendencies of the organ in question"./ We cannot 

 by excessive feeding make a giant out of the germ destined to 

 form a dwarf; we cannot, by means of exercise, transform the 

 muscles of an individual destined to be feeble into those of a 

 Hercules, or the brain of a predestined fool into that of a Leibnitz 

 or a Kant, by means of much thinking. With the same amount 

 of exercise the organ which is destined to be strong, will attain 

 a higher degree of functional activity than one that is destined to 

 be weak. Hence natural selection, in destroying the least fitted 

 individuals, destroys those which from the germ were fooMy dis- 

 posed./' Thus the result of exercise during the individual life does 

 not acquire so much importance, for, as compared with differences 

 in predisposition, the amount of exercise undergone by all the 

 individuals of a species becomes relatively iiniform. / The increase 

 of jin organ in the course of generations does not depend upon 

 the summation of the exercise taken during single lives, but 

 upon the summation of more favourable predispositions in the 

 germs. 



In criticizing these arguments, it may be questioned whether the 

 single individuals of a species which is undergoing modification do, 

 as a matter of fact, exercise themselves in the same manner and to 



