30 ORGANIC EVOLUTION 



in such a way as to give more perfect conformity to the 

 environmental conditions ; while in artificial selection the 

 modification is such as to make the altered form more per- 

 fectly suit the uses to which man -wishes to put it. The 

 results of artificial selection are usually more quickly seen ; 

 for the selection for breeding purposes of individuals with 

 the desirable qualities is generally more rigid than in nature, 

 where the more and the less adapted forms will for a time 

 breed side by side, the more perfect gradually predominat- 

 ing more and more. 



The extent of the 

 modification produced by 

 artificial selection is very 

 great in many cases. 

 Notice the common do- 

 mestic chickens, in which 

 FIG. 5. skuii of Polish fowl, showing the pe- the different breeds differ 



culiar knob that has been developed in front of the 



brain case. From Wright's New Book of Poultry, from One another tO SUCh 



by the courtesy of Cassell & Company. 



a degree that if they 



occurred in nature the several kinds would be referred not 

 only to different species, but to different genera (Plates 12-19 

 and Fig. 5). Compare the slender "game" (Plate 12, A\ 

 1 6, JB), which most closely of all resembles the ancestral 

 "jungle fowl" (Plate 16, A\ with the heavy " Brahma" (Plate 

 15, C, D] or " Cochin-china" (Plate 15, A, B\ 19, B\ or with 

 the long-tailed "Japanese" cocks (Plate 17), or with the little 

 "bantam" (Plate \\,D\ 19, C). Or notice the varieties of 

 pigeons, as shown in another illustration (Plate 20 and Fig. 6). 

 These races differ from one another anatomically and 

 in disposition as much as do natural species, yet in one 

 important particular they fail to resemble natural species. 



