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,! 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 
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 
