226 Evolution and Adaptation 
citing some cases amongst plants that have been changed 
directly by the action of the environment. He says that 
since plants have no motions they have consequently no 
habits, but they are developed by changes in their nutrition, 
etc., and this brings about the superiority of some of the 
vital movements over others. 
Amongst domestic animals Lamarck cites the case of the 
dog, that has come from a wild form like the wolf, but hav- 
ing been carried into different countries has acquired different 
and new habits, and this has led to the formation of new 
races, such as the bulldog, greyhound, pug-dog, spaniel, etc. 
Lamarck’s argument shifts so often back and forth from 
animals to plants, that it is clear that in his own mind he did 
not see any important difference between the action of the 
environment on plants, and the use of the organs of the 
animal. He gives in this same connection his oft-quoted 
summary of what he calls the two laws of nature “which 
observation always establishes.” 
First Law. In every animal, that has not passed beyond 
the term of its development, the frequent and sustained use 
of any organ strengthens it, develops it, increases its size, 
and gives it strength proportionate to the length of time of its 
employment. On the other hand, the continued lack of use of 
the same organ sensibly weakens it; it deteriorates, and its 
faculties diminish progressively until at last it disappears. 
’ Second Law. Nature preserves everything that she has 
caused the individual to acquire or to lose by the influence 
of the circumstances to which the race has been for a long 
time exposed, and consequently by the influence of the pre- 
dominant use of certain organs (or in consequence of its 
continued disuse). She does this by the generation of new 
individuals which are produced with the newly acquired 
organs. This occurs, provided that the acquired changes 
were common to the two sexes, or to the individuals that 
produced the new forms. 
