PRArTICAL LAWS (»1' LIFI-: 888 



everyone cooperated, beginning with present niunbers, or witli ten pairs, 

 to increase them to limits of insect and weed-seed food supitly ? 



Figuring the numl)er of buds prochiced l»y a grap«*, j>each, ai)pl<'. 

 strawberry, or other fruit, the number of eyes Ity a )>otat(), tlie numlxT 

 of seeds by a grain or vegetable plant, how long would it take to supply 

 every farm or garden with a favorable variation? This introduces us to 

 the second practical law uf life. 



» 



Law of variation. No ttm liritif/ f/ihit/s arr. cvactly alike 

 Can we liiid two forest leaves, blades of o-rass, or luiiiiaii 

 faces exactly alike ? Living organisms are too complicated 

 for it to happen, even by chance, that any two slionld be 

 alike. So this universal law of living nature has given us all 

 our different kinds of plants and animals. 



Domesticated plants and animals early attracted Daiwin's 

 attention as showing variations most clearly.^ Horses, cattle, 

 sheep, dogs, pigeons, and all manner of cultivated plants have 

 varied in the brief centuries of human control, and are still 

 varying, in most wonderful fashion. We have horses, from 

 C/lydesdales and Norman Percherons U) Shetland ponies, all 

 produced by human breeding and selection. Ages before 

 man appeared on tlie eartli little Eoliippus, not nuich larger 

 than a fox, with five toes, four of them hoofed, trotted over 

 the bogs of the tunes; and we can now trace in successive 

 strata of rocks how the modern horse developed from ibis 

 earliest form. The story of other animals and even of man 

 himself we have not as yet been able to trace so clearly. 



The great practical values attaching to variations in relation 

 to agricultural productions are touched ui)on in CliapUT IX. 

 Since these dei)end so largely upon the possibilities of increas- 

 ing and pro[)agating favoralde variations, we nnist considei- 

 this stibject further in connection with the greatest of all 

 biological laws. 



1 Darwin, Variations of Animals and Plants under Domestication. 



