darwin's theory. 13 



which is capable of indefinitely-continued, fertile repro- 

 duction, not only among its own individuals, but, pecu- 

 liarly so, with the individuals of any other variety of 

 the same species. Thus, an Arab horse, the English 

 race horse, the dray-horse, the Shetland pony, &c, 

 represent varieties, or breeds, of the species horse : 

 and a Fantail, a Pouter, a Carrier, a Runt, a Barb, 

 a Jacobin, &c, represent varieties of the Pigeon 

 species. 



The variation, modification, or improvement, occurring 

 under domestication, Darwin represents truly, as matter 

 of fact, to be very great. It is proved, by him, con- 

 clusively, that there is scarcely any part of the organ- 

 ization of any individual of any species of plant or ani- 

 mal, under domestication, which is not susceptible of 

 some, and, in the majority of instances, of great modi- 

 fication. Even the bones, and the internal organs — 

 the liver, the kidneys, the vertebrae, the reproductive 

 organs, the oesophagus, the intestinal canal — have been 

 shown to be greatly modified. Cases of increase, and 

 of decrease in the number of the vertebrae, have been 

 demonstrated to be of frequent occurrence. There are 

 improvements, or variations, in the legs, in the tongue, 

 in the eyes, in the skin, in the hair, in the feathers, in 

 the hoofs, in the horns, in the tail, and in the 

 wings. There are the greatest variations in the head. 

 Even the teeth have varied greatly, in number, size, 

 and other characters. 



Modifications, most favorable, and most different, in 

 character, have arisen, in a variety of ways, with birds 



of the same species ; in their head, or crest feathers, in 



2* 



