IGO DISTINCT SPECIES PRESENT Chap. V. 



in which both parents liave lost some character which ilieir 

 progenitor possessed, the tendency, Avliether stronf^ or -weak, 

 to reproduce the lost character might be, as was formerly re- 

 marked, for all that wc can sec to the contrary, transmitted 

 for almost any uuml:)cr of generations. When a character which 

 h;is been lost in a lu'ced, reappears after a gTcat immber of 

 generations, the most probable hypothesis is, not that the ofl- 

 spring suddenly takes after an ancestor removed by some hun- 

 dred generations, but that in each successive generation the 

 character in question has been lying latent, and at last, luidei 

 imknown favorable conditions, is developed. With the barb- 

 pigeon, for instance, which very rarely produces a blue bird, 

 it is probable that a latent tendency exists in each generation 

 to produce blue plumage. The possibility of chai'acters long 

 lying latent can be imderstood according to the hypothesis of 

 })angenesis, which I have given in another work. The abstract 

 improbability of a latent tendency being transmitted through 

 a vast number of generations, is not greater tlian that of quite 

 useless or rudimentary organs being thus transmitted. A mere 

 tendency to produce a nuHment is indeed sometimes inherited. 

 As all the species of the same genus are supposed, on our 

 theory, to be descended from a connnon progenitor, it might 

 be expected that they would occasionally vary in an analogous 

 manner; so that the varieties of two or more species would re- 

 semble each other, or that a variety of some one species would 

 resemble in certain characters another and distinct species — 

 this other species being, according to our view, only a well- 

 marked and permanent variety. But characters thus gained 

 would probably be of an unimportant nature, for the presence 

 of all important characters will be governed by natural selec- 

 tion, in accordance with tlic tlifTerent habits of the species, and 

 Avill not be left to the mutual action of the nature of tlie organ- 

 ism and of the conditions of life. It might further be expected 

 that the species of the same genus Avould occasionally exhil^it 

 reversions to long-lost ancestral characters. As, however, we 

 never know tlic exact character of the common ancestor of a 

 natural group, we could not distinguish these two cases : if, 

 iV)r instance, we did not know that the rock-pigeon was not 

 feather-footed or turn-crowned, we could not have told whether 

 these characters in our domestic breeds were reversions or only 

 analogous variations ; but wc might have inferred that the blue 

 color was a case of reversion from llie number of the markings, 

 whicli arc correlated with this tint, and which it docs not ap- 



