230 



ARID AGRICULTURE. 



IMPROVE- 

 MENT BY 

 DOMESTICA- 

 TION 



Until very recent times, indeed, agricultural 

 progress has been slow. As a rule, all life that 

 man has brought under domestication for his use 

 has been improved over its wild state. The one 

 exception (and it takes one exception to prove 

 the rule) seems to be the donkey, which an 

 Egyptian writer tells us has deteriorated much 

 from the character of the wild ass of Africa, 

 from which it sprung. Until the present day, 

 the improvement in our best developed breeds 

 of animals has not been as great as might be ex- 

 pected, and seems to have depended more on an 

 abundance of food than on breeding proper. The 

 profound changes which have occurred in plants 

 have no parallel in the animal kingdom. The 

 simple reason for this seems to center in the 

 difference of mere productiveness of plants and 

 animals, and in the fact that plants may be prop- 

 agated by vegetative parts, so that their perpetu- 

 ation does not depend on two parents and two 

 lines of mixed heredity. The principles of life 

 of development and growth, of variation and 

 change, are the same in both plants and animals, 

 but breeders can observe the lives of a vast num- 

 ber of plants compared with a limited number 

 of animals. Some of the most prolific animals, 

 like certain fishes and insects, have been little 

 subject to artificial breeding. The birds which 

 have been domesticated are the most prolific and 

 show the greatest variety, and improvement, evi- 



