10 



THE AMERICAN NATURALIST j Vol. XI. VI 



silver-tipped bear present instances of the whitening 

 process beginning with the hair tips. Becall, in this con- 

 nection, the lighter colors sometimes present on the hair 

 tips of the cattle crosses reported by Professor Went- 

 worth, and the "atomic" superficial tissues of the Silkie 

 fowl with its pigmented deeper tissues. Thus it seems 

 that with mammals and with some birds the whitening 

 process begins with the more superficial tissues and con- 

 tinues to the deeper ones; with mammals, coarse hair, 

 fine hair, skin, nail, sclerotic, iris, choroid, being the order 

 followed. 



Permit a short digression into the plant kingdom. Of 

 the two or three hundred varieties of the dent corn, all 

 of the yellow and red varieties have red cobs and all of 

 the white varieties have white cobs, with the exception of 

 St. Charles County white, which has a red cob. 



Jack-stock breeders in America are making an effort to 

 establish a race of black animals with white points, and 

 the following evidence, while primarily bearing on this 

 problem, is typical of the behavior when not involving 

 the whitening process of pigments of domestic animals. 

 In the Breeders' Gazette, May 10, 1911, a breeder states 

 this problem : 



color. He ,s ,x„, K ,)„. ,.„,„, nt lu . M1( >U|( , ^ ^ f 



jack in his locality and n first-class mule-getter. Is this color a real 



^ To which L. M. Monsees, of Sedalia, Mo., the jack-stock 



Thus it seems probable that, when different parental 

 pigments, but not the whitening process, are involved, the 



