300 LAMARCK, HIS LIFE AND WORK 
dispersed by man into different countries, with differ- 
ent climates; and after a time these same individuals, 
having undergone the influences of their habitats, and 
of the different habits they were obliged to contract 
in each country, have undergone remarkable changes, 
and have formed different special races. Now, the 
man who, for commercial reasons or from interests of 
any other kind, travels a very great distance, having 
carried into a densely populated place, as for example 
a great capital, different races of dogs originated in 
some very distant country, then the increase of these 
races by heredity (génération) has given rise succes- 
sively to all those we now know. 
“The following fact proves, as regards plants, how 
a change in any important circumstance leads to a 
change in the parts of their organisms. 
“So long as Ranunculus aquatilis is submerged 
in the water, its leaves are all finely incised and the 
divisions hair-like; but when the stalks of this plant 
reach the surface of the water, the leaves which grow 
out in the air are wider, rounded, and simply lobed. 
If some feet from the same plant the roots succeed 
in pushing into a soil only damp, without being sub- 
merged, their stalks then are short, none of their 
leaves are divided into capillary divisions, which gives 
rise to Ranunculus hederaceus, which the botanists 
regard as a species whenever they meet with it. 
“There is no doubt that as regards animals im- 
portant changes in the circumstances under which 
they are accustomed to live do not produce altera- 
tion in their organs; for here the changes are much 
slower in operating than in plants, and, consequently, 
are to us less marked, and their cause less recog- 
nizable. 
“As to the circumstances which have so much 
power in modifying the organs of living beings, the 
most influential are, doubtless, the diversity of the 
surroundings in which they live; but besides this 
