234 DOMESTIC PIGEONS. Chap. VI. 



unless these parts happened to vary under domestication : 

 I do not positively assei't that this is the case, although I 

 have seen traces of such variability in the wing-feathers, and 

 certainly in the tail-feathers. It would be a strange fact if 

 the relative length of the hind toe should never vary, seeing 

 how variable the foot is both in size and in the number of 

 the sciitelltB. "With respect to the domestic races not roosting 

 or building in trees, it is obvious that fanciers wouLi never 

 attend to or select such changes in habits ; but we have seen 

 that the pigeons in Egypt, which do not for some reason 

 like settling on the low mud hovels of the natives, are led, 

 apparently by compulsion, to perch in crowds on the trees. 

 We may even affirm that, if our domestic races had become 

 greatly modified in any of the above specified respects, and it 

 could be shown that fanciers had never attended to such 

 points, or that they did not stand in correlation with other 

 selected characters, the fact, on the principles advocated in 

 this chapter, would have offered a serious difficulty. 



Let us briefly sum up the last two chapters on the pigeon. 

 We may conclude with confidence that all the domestic races, 

 notwithstanding their great amount of difference, are de- 

 scended from the Columba livia, including under this name 

 certain wild races. But the diiferences between the latter 

 throw no light whatever on the characters which distinguish 

 the domestic races. In each breed or sub-breed the individual 

 birds are more variable than birds in a state of nature ; and 

 occasionally they vary in a sudden and strongly-marked 

 manner. This plasticity of organization apparently results 

 from changed conditions of life. Disuse has reduced certain 

 parts of the body. Correlation of growth so ties the organisa- 

 tion together, that when one part varies other parts vary at 

 the same time. When several breeds have once been formed, 

 their intercrossing aids the progress of modification, and has 

 even produced new sub-breeds. But as, in the construction 

 of a building, mere stones or bricks are of little avail without 

 the builder's att, so, in the production of new races, selection 

 has been the presiding power. Fanciers can act by selection 

 on excessively slight individual difi'erences, as well as on 

 those greater differences which are called sports. Selection 



