Page:Evolution of Life (Henry Cadwalader Chapman, 1873).djvu/199

Rh individuals of one and the same species remain mostly very similar."

Every one is aware that favorite breeds of cattle, many beautiful flowers, particular kinds of horses, such as the dray-horse, race-horse; etc., are not found in a wild state, but that these forms have been gradually produced. Let us examine the means by which this end has been accomplished. Suppose, for example, a gardener wishes so to modify some particular white flower that in time it will exhibit a striking scarlet color. He looks carefully among the particular flowers until he finds one which offers a trace of red; he plants the seeds of this flower, and from their posterity he selects the reddest flowers. Continuing to select the reddest flowers, and planting their seeds alone, finally the gardener succeeds in obtaining one of a scarlet color. The success of the gardener's operation depends upon the fact of there appearing, among the flowers which are usually white, one exhibiting a faint red color, and upon the fact of posterity inheriting from their parents a variation which they transmit in turn to their offspring, this variation becoming more marked as it is transmitted from generation to generation. An equally good illustration of this principle is the often-quoted instance of Seth Wright, the Massachusetts farmer, who, noticing that one of his rams, with a long body and short bandy legs, could not jump over the fences, concluded that it would be a good thing to breed with this ram alone, and to his great satisfaction soon obtained a race of sheep characterized by the peculiarity of a long body and short bandy legs. Indeed, although the subject of inheritance is still theoretically obscure, practically it is so well understood that Sir John Sebright "can produce in three years a given feather, but that he requires six years in order to obtain a particular kind of head and beak." Now we