xii.] THE ORIGIN OF SPECIES. 235 



experience of cattle-breeders, stock-farmers, horse-dealers, and 

 dog and poultry fanciers. Nay, it is only the other day that an 

 eminent physiologist, Dr. Brown-Sequard, communicated to the 

 Royal Society his discovery that epilepsy, artificially produced in 

 guinea-pigs, by a means which he has discovered, is transmitted 

 to their offspring. 



But a race, once produced, is no more a fixed and immutable 

 entity than the stock whence it sprang ; variations arise among 

 its members, and as these variations are transmitted like any 

 others, new races may be developed out of the pre-existing one 

 ad infinitum, or, at least, within any limit at present determined. 

 Given sufficient time and sufficiently careful selection, and the 

 multitude of races which may arise from a common stock is as 

 astonishing as are the extreme structural differences which they 

 may present. A remarkable example of this is to be found in 

 the rock-pigeon, which Mr. Darwin has, in our opinion, satis 

 factorily demonstrated to be the progenitor of all our domestic 

 pigeons, of which there are certainly more than a hundred well- 

 marked races. The most noteworthy of these races are, the four 

 great stocks known to the &quot; fancy &quot; as tumblers, pouters, carriers, 

 and fantails ; birds which not only differ most singularly in size, 

 colour, and habits, but in the form of the beak and of the skull : 

 in the proportions of the beak to the skull ; in the number of 

 tail-feathers; in the absolute and relative size of the feet; in 

 the presence or absence of the uropygial gland ; in the number 

 of vertebrae in the back ; in short, in precisely those characters in 

 which the genera and species of birds differ from one another. 



And it is most remarkable and instructive to observe, that 

 none of these races can be shown to have been originated by the 

 action of changes in what are commonly called external circum 

 stances, upon the wild rock-pigeon. On the contrary, from time 

 immemorial, pigeon fanciers have had essentially similar methods 

 of treating their pets, which have been housed, fed, protected 

 and cared for in much the same way in all pigeonries. In fact, 

 there is no case better adapted than that of the pigeons to 

 refute the doctrine which one sees put forth on high authority, 



