DARWIN AND NATURAL SELECTION 47 



tain species. They differ in shape, color, size and in- 

 stincts. For example, there are the carrier-pigeons, 

 with their special topographical instinct; the tum- 

 blers, which are in the habit of flying at a great 

 height in compact flock and then tumbling in the air 

 head over heels ; the f antails, whose tail, owing to the 

 disposition of its feathers, resembles that of a pea- 

 cock; others have tufts of feathers, peculiar creases 

 of the skin, modified beaks or feet, etc., etc. 



Darwin secured specimens of every available breed 

 from all parts of the world. He became acquainted 

 with the best known breeders and fanciers, joined 

 pigeon clubs, and after years of observation, suc- 

 ceeded in proving that all the various breeds (which 

 breeders believed to be derived from as many wild 

 species) were all descended from one single species, 

 the European rock pigeon (Columba livia) . *, 



What breeders do on purpose, Nature does uncon- 

 sciously and her aim is attained through "the struggle 

 for life," i. e., the struggle of animals or plants against 

 certain conditions of the inorganic world ( frost, heat, 

 dearth, etc.), the struggle of the --individual against 

 individuals of different species on which it preys or 

 whose prey it may become, and the struggle against 

 other individuals of the same species for a place at 

 Nature's banquet table. 



Darwin illustrates in his book the way in which cer- 

 tain species would surely overrun the earth if some 



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