Chap. V.] HIGHLY VARIABLE. 187 



seriously shaken my belief in its truth, had not the 

 great variability in plants made it particularly difficult 

 to compare their relative degrees of variability. 



When we see any part or organ developed in a 

 remarkable degree or manner in a species, the fair 

 presumption is that it is of high importance to that 

 species : nevertheless it is in this case eminently liable 

 to variation. Why should this be so ? On the view 

 that each species has been independently created, with 

 all its parts as we now see them, I can see no explana- 

 tion. But on the view that groups of species are 

 descended from some other species, and have been 

 modified through natural selection, I think we can 

 obtain some light. First let me make some preliminary 

 remarks. If, in our domestic animals, any part or the 

 whole animal be neglected, and no selection be applied, 

 that part (for instance, the comb in the Dorking fowl) 

 or the whole breed will cease to have a uniform 

 character: and the breed may be said to be degenera- 

 ting. In rudimentary organs, and in those which have 

 been but little specialised for any particular purpose, 

 and perhaps in polymorphic groups, we see a nearly 

 parallel case ; for in such cases natural selection either 

 has not or cannot have come into full play, and thus 

 the organisation is left in a fluctuating condition. But 

 what here more particularly concerns us is, that those 

 points in our domestic animals, which at the present 

 time are undergoing rapid change by continued selec- 

 tion, are also eminently liable to variation. Look at 

 the individuals of the same breed of the pigeon, and 

 see what a prodigious amount of difference there is in 

 the beaks of tumblers, in the beaks and wattle of 

 carriers, in the carriage and tail of fantails, &c, these 



