DARWIN'S SPECIFIC VARIATION. 127 



ancestor) of all domestic breeds of pigeons, 

 the change in colour arising from crossing 

 two breeds may become intelligible. 



The Specific life-force of almost any two 

 breeds of pigeons must be very similar, 

 and to produce a change in colour from 

 that of an antecessor, would involve merely 

 a slight modification of that portion of the 

 organisation that determines the colour of 

 the feathers. If now, in crossing birds of 

 different colours, these colour forces blend, 

 the result, as in the mixing of two paints, 

 may be a colour different from either of the 

 parents ; or if the forces do not blend, may 

 they not neutralise each other, and allow 

 the colour of the remote antecessor to assert 

 itself? 



In discussing the question whether dom- 

 estic breeds of pigeons are descended from 

 one or from several wild species, Darwin 

 says he has been greatly struck by the fact, 

 that every breeder of cattle is firmly con- 

 vinced that the breed he has cultivated is 

 descended from a distinct aboriginal species, 

 and the explanation of this delusion he thinks 

 simple. "From long -continued study," he 

 says, " they are strongly impressed with the 

 difference between the several races, and they 

 well know that each race varies slightly, and 



