398 



THE AMEBIC AN NATURALIST [Vol. LI 



In the Wyandotte group of species, the texture of the 

 comb is very different in the blue kind from what it is in 

 the silver Wyandotte. The length of the tail feathers 

 differs very much in the different breeds. The white 

 Wyandotte lays dark brown eggs, the silver Wyandotte 

 lays salmon-colored eggs with minute white spots, the 

 black Wyandotte lays white eggs. 



It is very rare for new species in chickens and pigeons 

 to come up to the quality of old established ones, unless 

 the fashion or standard happens to change. The shape 

 and carriage of the tail, and the general shape of the body 

 are very much better in white Fantail pigeons than in the 

 newer black- tailed whites or white- tailed blacks. And the 

 shape of the new blue Wyandotte is not yet what it is in 

 the white and the silver. 



We know of only a few instances of new dog or poultry 

 species being bred from hybrids inter se. In those cases 

 the breeders had no very definite object in view to start 

 with. This mode of origin of species under domestication 

 is certainly not the common one. Species of cultivated 

 animals are commonly being changed by a very notice- 

 able conscious selection. The variability necessary for 

 improvement is continually kept up, sometimes by de- 

 liberate, but mostly by a kind of unintentional crossing, 

 that is to say by admitting exceptionally fine offspring 

 produced by matings of hybrids back to the species, into 

 the registry. On the other hand, automatic purification, 

 automatic reduction of the heightened potential variabil- 

 ity, is the necessary outcome of the fact that only very 

 few and very exceptionally "good" males are used as 

 breeders. 



Species of tame animals, especially fertile ones as 

 chickens, are easily kept apart so that excessive splitting 

 up into secondary species is possible and even the rule. 

 For in^taTi('(\ in those species in which a certiiin much 

 soimlit •junlity i> influenced by the internal secretion of 

 tlic .-('x-nlaiiils. it is obviously impossible to make a pure 

 strain in which both males and females come up to one 



