Inheritance of Acquired Characters 225 



different modes of multiplication and of regeneration have 

 arisen, and these have been conserved. 



5. That with the aid of sufficient time and of favorable 

 circumstances the changes that have taken place on the sur- 

 face of the globe have called forth new structures and new 

 habits, and in consequence have modified the organs of the 

 body, and made animals and plants such as we see them at 

 the present day. 



6. Finally, as a result of these changes that living bodies 

 have been forced to undergo, species have been formed, but 

 these species have only a relative constancy, and are not as 

 ancient as is nature herself. If the environment remains the 

 same, species also remain the same, as is exemplified by the 

 animals living at present in Egypt, which are exactly like 

 those living there in ancient times. 



Lamarck concludes that the appearance of stability is 

 always mistaken by the layman for the reality, because, in 

 general, every one judges things relatively to himself. In 

 fact, species are not absolutely constant, but are so only 

 temporarily. "The influence of the environment is con- 

 tinuous and always active, but its effects may only be 

 recognized after a long time." The irregularity and the 

 complexity of the organization of animals is the outcome of 

 the infinitely diversified circumstances to which they have 

 been subjected. These changes, Lamarck claims, do not 

 directly cause modifications in the form of animals, 1 but 

 bring about changes in their needs, and changes in their 

 needs bring about changes in their actions. If the needs 

 remain the same, the acquired actions become habits. These 

 habitual actions lead to the use of certain parts in preference j 

 to others, and this in turn to an alteration in form and struc- : 

 ture. The individuals so changed breed together and leave 

 descendants that inherit the acquired modification. 



Curiously enough, Lamarck follows up this argument by 



1 This is clearly meant to be applied only in the case of higher animals. 

 Q 



