44 COAT CHARACTERS IN GUINKA-PIGS AND RABBITS. 



condition of reduction. The successive steps by which the pigmenta- 

 tion of guinea-pigs undergoes reduction are about as follows: (i) The 

 pigment centers are all functional, but the pigment areas do not quite 

 meet along the middle of the ventral surface, or in the forehead. Per- 

 haps the pigment fails to reach one or more of the feet also. (2) One 

 or both shoulder patches are wanting, producing the Dutch-marked 

 type (compare fig. 6, p. 12). (3) The side patches are also wanting; only 

 the rump and sides of the head are pigmented (fig. 2, p. 10). (4) The 

 rump patch disappears ; only the sides of the head are pigmented, and 

 here the patches are small, or one or more of them may be wanting 

 (fig. 4, p. n). An extreme condition of this sort is represented by 

 c? 721 , whose coat was entirely unpigmented except for a small patch of 

 black about 5 mm. square on the outer surface of his right ear. (5) 

 The skin is wholly unpigmented, though the eyes are as in all the fore- 

 going stages dark. One can by selection progress in either direction 

 through this series of changes, either increasing or decreasing the 

 number and extent of the pigment patches, but it is impossible without 

 long-continued selection to fix the color pattern at any particular stage in 

 the series ; perhaps it is wholly impossible to do so, as Cu6not ( : 04, p. LV) 

 asserts on the basis of his studies on mice, but this I very much doubt. 

 I doubt it first, because we do find color patterns of this sort firmly fixed 

 in many wild species, such as antelopes, skunks, etc. ; secondly, and still 

 more, I doubt it because of what we see accomplished in domesticated 

 animals. Take the case of cattle alone. Different breeds of cattle have 

 often distinctive color patterns, as well as specific pigments in their 

 coats. Holstein cattle are white, marked with large but more or less 

 irregular black spots, the color pattern being apparently not definitely 

 fixed. Dutch belted cattle, probably derived from the same general 

 source as the Holstein, have for a long time been subjected to a rigid 

 selection for a more definite color pattern, viz, an animal wholly black 

 except for a broad white belt around the middle of the body. To this 

 type the breed is said to keep very true. 



Pure-bred Hereford cattle as kept at the present time in America 

 are red over the greater part of the body, but are invariably white- 

 faced ; a longitudinal white stripe extends down the middle of the 

 back, and the belly and flanks are more or less extensively marked 

 with white. The white face, though now rigidly insisted upon and 

 always seen in pure-bred herds, has not always been so common in the 

 breed. A half century or more ago, according to Shaw ( : 03), rival 

 breeders advocated white-faced and mottled-faced Herefords, but the 

 former prevailed, and by continued selection the mottled-faced con- 

 dition has now apparently been eliminated from the breed. 



These cases indicate that certain of the typical color patches, as, for 

 example, the cheek patches of cattle, can by continued selection be 



