384 



PLANT AND ANIMAL BREEDING 



Artificial Selection. — Darwin reasoned that if nature seizes 

 upon favorable variants, then man, by selecting the variations he 

 wanted, could form new varieties of plants and animals much more 

 quickly than nature. No one can doubt, when we compare the im- 

 proved breeds of dogs 

 with the original wild 

 dog, or cultivated fruits 

 like the apple and peach 

 with their wild ances- 

 tors, that man has done 

 much in the way of im- 

 proving domesticated 

 plants and animals. 

 But how has this been 

 accomplished ? 



Every farmer knows 

 that to produce good 

 results he must first 



Improvement in corn by selection. At the left, 

 the corn improved by selection frorai the original 

 type at the right. 



10 



14 IS 16 



have good seed or good stock. The plants or animals must come 

 from sturdy parents. Then they must have favorable conditions 



in which to grow, or they 

 will not produce. They 

 must have care. On aban- 

 doned farms the plants 

 soon tend to revert or go 

 back to wild conditions. 

 And if we are to produce 

 better plants and animals, 

 we must continually select 

 the best products for 

 breeding as well as give 

 them the best environ- 

 ment possible. 



Two Kinds of Variations 

 Occur. — Variations in na- 

 ture appear to be of two 

 large number of peas or 



-pn 



/ 2 18 101 151 98 29 4 1 = 405 



00 



8mm. 9mm. lOmm. Ilmm. IBmm. 13mm. 14mm. ISmm. 16mm. 

 These columns represent the numbers of 

 beans of the different sizes. For these 405 

 beans, Quetlet's curve would be a curved line 

 joining the tops of the columns. 



sorts. If we measure the size of a 



beans, we find that though most of them are of a certain size 



