CHARLES EGBERT DARWIN. 377 



clover, as other bees cannot reach the nectar. . . 

 Hence we may infer as highly probable that, if the 

 whole genus of humble-bees became extinct or 

 very rare in England, the heart's-ease and red clover 

 would become very rare, or wholly disappear. The 

 number of humble-bees in any district depends in 

 a great measure upon the number of field-mice, 

 which destroy their combs and nests ; the number 

 of mice is largely dependent, as every one knows, 

 on the number of cats." Hence, as Mr. Darwin 

 shows, the frequency of certain flowers in a district 

 may depend upon the number of cats ! 



Darwin showed, by most interesting experiments 

 with pigeons, that the various breeds come from 

 the wild rock-pigeon ; that dogs are descended, 

 probably, from the wolf; that different varieties 

 can be produced and perpetuated under changing 

 conditions of life ; that species are only well 

 marked and permanent varieties. He showed how 

 organs can be changed by use or disuse ; such as, 

 the erect ears of wild animals become drooping 

 under domestication ; or moles have only rudi- 

 mentary eyes, covered with skin or fur, because 

 not needed for sight. 



In the " Origin of Species," the theory of evolu- 

 tion received proof which was so nearly incontro- 

 vertible that the subject was brought prominently 

 before the world as never before. Mr. Alfred 

 Kussell Wallace, an able scientist, came to the 

 same conclusion as Darwin in regard to the power 

 of " Natural Selection," and published, at the same 



