Seite - 168 - in The Origin of Species

168 ORIGIN OF SPECIES variations in the same parts having been accumulated by natural and sexual selection, and having been thus adapted for secondary sexual, and for ordinary purposes. Distinct Species present analogous Variations, so that a Variety of one Species often assumes a Character proper to an allied Species, or reverts to some of the Characters of an early Progenitor.—These propositions will be most readily understood by looking to our domestic races. The most dis- tinct breeds of the pigeon, in countries widely apart, present sub-varieties with reversed feathers on the head, and with feathers on the feet,—characters not possessed by the abo- riginal rock-pigeon; these then are analogous variations in two or more distinct races. The frequent presence of four- teen or even sixteen tail-feathers in the pouter may be con- sidered as a variation representing the normal structure of another race, the fantail. I presume that no one will doubt that all such analogous variations are due to the several races of the pigeon having inherited from a common parent the same constitution and tendency to variation, when acted on by similar unknown influences. In the vegetable king- dom we have a case of analogous variation, in the enlarged stems, or as commonly called roots, of the Swedish turnip and Ruta baga, plants which several botanists rank as varie- ties produced by cultivation from a common parent: if this be not so, the case will then be one of analogous variation in two so-called distinct species; and to these a third may be added, namely, the common turnip. According to the ordi- nary view of each species having been independently created, we should have to attribute this similarity in the enlarged stems of these three plants, not to the vera causa of com- munity of descent, and a consequent tendency to vary in a like manner, but to three separated yet closely related acts of creation. Many similar cases of analogous variation have been observed by Naudin in the great gourd-family, and by various authors in our cereals. Similar cases occurring with insects under natural conditions have lately been discussed with much ability by Mr. Walsh, who has grouped them under his law of Equable Variability. With pigeons, however, we have another case, namely, the occasional appearance in all the breeds, of slaty-blue