382 BIOLOGY AND ITS MAKERS 



under the name of laws, which have been translated by 

 Packard as follows: 



" First Law : In every animal which has not exceeded the 

 term of its development, the more frequent and sustained 

 use of any organ gradually strengthens this organ, develops 

 and enlarges it, and gives it a strength proportioned to the 

 length of time of such use; while the constant lack of use of 

 such an organ imperceptibly weakens it, causing it to become 

 reduced, progressively diminishes its faculties, and ends in 

 its disappearance. 



" Second Law : Everything which nature has caused 

 individuals to acquire or lose by the influence of the circum- 

 stances to which their race may be for a long time exposed, 

 and consequently by the influence of the predominant use of 

 such an organ, or by that of the constant lack of use of such 

 part, it preserves by heredity and passes on to the new indi- 

 viduals which descend from it, provided that the changes 

 thus acquired are common to both sexes, or to those which 

 have given origin to these new individuals. 



" These are the two fundamental truths which can be mis- 

 understood only by those who have never observed or 

 followed nature in its operations," etc. The first law 

 embodies the principle of use and disuse, the second law that 

 of heredity. 



In 181 5 his theory received some extensions of minor 

 importance. The only points to which attention need be 

 called are that he gives four laws instead of two, and that a 

 new feature occurs in the second law in the statement that 

 the production of a new organ is the result of a new need 

 (besoin) which continues to make itself felt. 



Simplified Statement of Lamarck's Views. — For practical 

 exposition the theory maybe simplified into two sets of facts: 

 First, those to be classed under variation; and, second, those 

 under heredity. Variations of organs, according to Lamarck, 



