140 t>ISTINOT SPECIES PRESENT 



go on varying than parts which have long been inherited 

 and have not varied, to natural selection having more or 

 less completely, according to the lapse of time, overmastered 

 the tendency to reversion and to further variability, to sex- 

 ual selection being less rigid than ordinary selection, and to 

 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 CHARAC- 

 TER 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 distinct 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 aboriginal rock-pigeon ; 

 these then are analogous variations in two or more distinct 

 races. The frequent presence of fourteen or even sixteen 

 tail-feathers in the pouter may be considered as a variation 

 representing the normal structure of another race, the fan^ 

 tail. I presume that no one will doubt that all such analo- 

 gous variations are due to the several races of the pigeon 

 having inherited from a common parent the same constitu- 

 tion and tendency to variation, when acted on by similar 

 unknown influences. In the vegetable kingdom we have a 

 case of analogous variation, in the enlarged stems, or as com- 

 monly called roots, of the Swedish turnip and ruta-baga, 

 plants which several botanists rank as varieties 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 ordinary view of 

 each species having been independently created, we should 

 have to attribute this similar^ in the enlarged stems of 

 these three plants, not to the vera causa of community of 

 descent, and a consequent tendency to vary in a like manner, 

 but to three separate 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 



