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 {g^n&ation) 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 thei^ 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 



