392 NINETEENTH CENTURY. PT. in. 



which might have come from the same parent, and he con- 

 cluded that the only difference was that some had branched 

 off from the common stock earlier than others, and so had 

 become more unlike just as brothers and sisters are very 

 like each other while distant cousins are much less liable to 

 have the same features and expression. 



The more we know of animals and plants, said La- 

 marck, the more difficult we find it to settle which are 

 related to each other and which are not. Linnaeus had long 

 ago pointed out that among plants which are well known, 

 such as the willows in Europe, the cactuses in South 

 America, and the heaths and everlastings at the Cape, there 

 are so many kinds differing very little from each other that it 

 is impossible to say which ought to be considered as separate 

 species and which as the descendants of one kind of plant. 



Moreover, we know how much plants and animals are 

 sometimes altered even in a few years. For example, by 

 growing in a drier soil or up a high mountain, plants 

 become stunted and altered in many ways, while birds when 

 shut up lose the power of using their wings, as has been the 

 case with our domestic poultry. Man can make a number 

 of different varieties both of plants and animals by merely 

 keeping those which have the peculiarities he admires. The 

 different kinds of pigeon, for example the pouters, fan-tails, 

 tumblers, and others, which are so unlike each other are 

 said by naturalists to be all descendants of the common 

 rock-pigeon ; and all the varieties of rabbit have come from 

 one wild species. You cannot find a wild pigeon with a 

 fan-tail, or a wild rabbit with lop-ears. 



If man, then, in a few hundred years can make such 

 changes, ' is it not possible,' said Lamarck, ' that nature in 

 all the long ages during which the world has existed, may 



