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 



