CH. XXXVIII. MODIFICATION OF ORGANS. 393 



have produced the different kinds of plants and animals by 

 gradually enlarging one part and diminishing another to suit 

 the wants of each?' These and many other arguments 

 Lamarck brought forward in his work in 1801, and again in 

 his * Philosophic Zoologique ' in 1809, to prove that the way 

 in which the Creator has formed different plants and animals 

 has been by altering them gradually out of simple forms. 



There was, however, one very weak point in all his argu- 

 ments ; he did not show sufficiently what should cause living 

 beings to go on altering, and becoming more and more dif- 

 ferent. For if you turn plants and animals, which man has 

 altered, out into the fields again, in a very few generations 

 they return very nearly to their old forms ; nor can we see 

 any reason why the differences between animals should go 

 on increasing unless they were picked out and kept apart, 

 as men keep them when they want to get new varieties. 



Lamarck did, indeed, point out that climate and dif- 

 ference of food would help to alter the nature of an animal, 

 but the chief reason he gave for changes taking place in 

 them, was that the animal itself might cause the alteration in 

 its form ; as for instance, a giraffe constantly wishing to eat the 

 boughs off high trees might stretch his neck, and so by de- 

 grees each generation might have longer necks than the last 

 one. This reason was so weak and ridiculous that it prevented 

 naturalists from paying much attention to Lamarck's theory. 



Geofiroy St.-Hilaire points out that the Farts or 

 Organs are the same in all Animals, only Modified to 

 snit their Wants. — Nevertheless Geoffroy St.-Hilaire was 

 inclined to think there was some truth in this theory, although 

 Cuvier was strongly against it. Cuvier, you remember, had 

 given his time chiefly to the restoration of the skeletons of 

 the higher animals, and he was as much struck withthe im- 



