EXCURSIONS OF AN EVOLUTIONIST 



Are there any instances in which the forms of 

 plants and animals have actually been seen to 

 vary, and, if there are, what seems to have been 

 the principal cause of variation in these in- 

 stances ? The answer is not far to seek. The 

 instances are very numerous indeed in which 

 variations and very marked ones, too have 

 been wrought in the characteristics of plants and 

 animals through the agency of man. The phe- 

 nomena of variation presented by animals and 

 plants under domestication are so numerous and 

 so complex that it would require many volumes 

 to describe them. Dogs, horses, pigs, cattle, 

 sheep, rabbits, pigeons, poultry, silk-moths, ce- 

 real and culinary plants, fruits and flowers innu- 

 merable, have been reared and bred by man for 

 many long ages, some of them from time im- 

 memorial. These domesticated organisms man 

 has caused to vary, in one direction or another, 

 to suit his natural or artificial needs, or even the 

 mere whim of his fancy. The variations, more- 

 over, which have thus been produced have been 

 neither slight nor unimportant, and have been 

 by no means confined to superficial characteris- 

 tics. Compare the thorough-bred race- horse 

 with the gigantic London dray-horse on the one 

 hand, and the Shetland pony on the other ; or, 

 among pigeons, contrast the pouter with the fan- 

 tail, the barb, the short-faced tumbler, or the ja- 

 cobin, all of which are historically known to have 



