36 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



breeders for the production of numerous varieties 

 subsequently becoming fixed by heredity among 

 the races of domestic animals, such as pigeons, cattle, 

 pigs, horses, dogs, etc. In nature a natural selec- 

 tion would occur, much more slowly, no doubt, 

 among animals in a wild state, and under the 

 exclusive influence of the struggle for life would 

 bring about the extinction of the forms less 

 fitted to maintain this struggle, and, at the same 

 time, the survival of such new variations as were 

 more adapted to the surrounding conditions. By 

 the side of this principal factor in evolution other 

 causes such as the influence of habits, or the more 

 direct one of the environment act only a subor- 

 dinate part not easy to define. 



Darwinism may with good reason be taxed with 

 being in this respect too exclusive, and with rather 

 misunderstanding the importance of the transforming 

 influences brought to light by the French scholars 

 Lamarck and Geoffroy-Saint-Hilaire, whose works 

 we have just analyzed. The Struggle for Life of 

 Darwin, very attractive as an explanation of the 

 extinction of species, and even of the disappearance 

 of intermediate varieties, takes no account of the 

 production of new variations so little, indeed, that 

 Darwin is compelled to relegate this point to simple 

 chance, that is to say, to the unknown. 



On the other hand Darwin's work is much more 

 exact, and especially much better supported by 

 proofs, than those of his predecessors. Endowed with 

 a marvellously observant mind, which extensive 

 travel had early sharpened and developed, ready 

 to grasp and set forth clearly the complicated 



