PRESIDENTIAL ADDRESS. 17 



3d. That every new need necessitating new actions to satisfy 

 it requires of the animal experiencing it either the more fre- 

 quent employment of such of its organs of which it previously 

 made less use, which develops and enlarges considerably, or 

 else the employment of new parts to which the needs insensi- 

 bly give rise within it through efforts of its internal sense."* 



In all this Lamarck does not expressly say that these trans- 

 formations are perpetuated by heredity, although this is clearly 

 implied, otherwise they would not be permanent. But he now 

 proceeds to embod}^ the general principle in what he calls a 

 law, the first law of organic life, to which he adds a second law 

 in which the principle of heredity is distinctly formulated. Al- 

 though these two great Lamarckian laws have been frequently 

 quoted in biological discussions, especially within the past three 

 or four years, it seems essential to the completeness of the 

 present exposition to introduce them. They are as follows : 



First Law : "In every animal which has not passed the limit 

 of its development the more frequent and sustained exercise 

 {emploi) of any organ gradually strengthens that organ, de- 

 velops and enlarges it, and gives it a power proportioned to the 

 duration of such exercise ; while the continued lack of exercise 

 {usage) of an organ gradually enfeebles it, deteriorates it, 

 progressively diminishes its power, and finally causes it to dis- 

 appear." 



Second Law : ' 'All that nature has caused individuals to ac- 

 quire or to lose through the influence of the circumstances to 

 which their race has found itself for 'a long time exposed, and 

 consequently, through the predominant exercise of certain or- 

 gans, or through a failure to exercise certain parts, it preserves 

 through heredity {generation) to the new individuals that are 



^ e 



*Op. fit., Vol. I, pp. 234-235. 



