Chap.V. laws of variation. 161 



distant, but that in each successive generation there has 

 been a tendency to reproduce the character in question, 

 which at last, under unknown favourable conditions, 

 gains an ascendancy. For instance, it is probable that 

 in each generation of the barb-pigeon, which produces 

 most rarely a blue and black-barred bird, there has 

 been a tendency in each generation in the plumage to 

 assume this colour. This view is hypothetical, but could 

 be supported by some facts ; and I can see no more 

 abstract improbability in a tendency to produce any cha- 

 racter being inherited for an endless number of genera- 

 tions, than in quite useless or rudimentary organs being, 

 as we all know them to be, thus inherited. Indeed, we 

 may sometimes observe a mere tendency to produce a 

 rudiment inherited : for instance, in the common snap- 

 dragon (Antirrhinum) a rudiment of a fifth stamen so 

 often appears, that this plant must have an inherited 

 tendency to produce it. 



As all the species of the same genus are supposed, 

 on my theory, to have descended from a common parent, 

 it might be expected that they would occasionally vary 

 in an analogous manner ; so that a variety of one species 

 would resemble in some of its characters another species ; 

 this other species being on my 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 selection, in accordance with the diverse 

 habits of the species, and will not be left to the mutual 

 action of the conditions of life and of a similar in- 

 herited constitution. It might further be expected 

 that the species of the same genus would occasionally 

 exhibit reversions to lost ancestral characters. As, how- 

 ever, we never know the exact character of the common 

 ancestor of a group, we could not distinguish these two 



