MENDELISM IN DOMESTIC ANIMALS 471 
be disposed of. As the type becomes well established and there is a wide 
field of choice among the grays the selection should be further refined by 
disposing of both parents of any foal of a color other than gray. By this 
method it should be a simple matter to establish a gray breed of draft 
horses which would not only breed true to color among themselves, but 
would also give only gray foals when mated to bay, brown, black, or 
chestnut horses. 
Mendelism in cattle. The state of knowledge of the inheritance of 
coat color in cattle is even less satisfactory than that in horses, but there 
are some results from experimental investigations which have firmly 
grounded our knowledge of certain points of it. 
White is a natural starting point in the discussion of Mendelian 
inheritance of coat color in cattle, but it proves to be by no means capable 
of simple treatment. The difficulty of dealing with white in cattle appears 
to be due to the variety of whites of different genotypes which are met 
with. Thus the white of Shorthorn cattle is apparently never a true 
white, for the eyelashes, face bristles, and particularly the ears always 
bear some red hairs, although often so few that they are ordinarily over- 
looked by breeders. This type of pigmentation is not an extreme con- 
dition of red and white blotching which is often met with in Shorthorn 
cattle, but it is entirely independent of spotting. This is indicated by 
the clean cut segregation which this type of coloration exhibits. 
Lloyd-Jones and Evvard present data which favors the explanation that 
white with colored extremities depends on a recessive extension factor, e. 
Another type of white met with in modern breeds appears to be merely 
an extreme condition of spotting. Such whites are not uncommon 
among Ayrshire and Holstein-Fresian cattle, but they are undoubtedly 
genetically different from whites with colored extremities. The wild 
white Park cattle of Britain and the white feral herds mentioned by 
Darwin always have colored ears, but it is doubtful whether they are 
genetically identical with the white Shorthorn. They apparently 
produce colored calves at times in spite of the fact that such calves are 
never retained in the breeding herds. It is known that some of these 
white herds were of mixed origin, and that some of them are creamy 
white rather than pure white. Accordingly it is not impossible that the 
colored calves which are produced by wild Park cattle are the result of 
recombinations of complementary factors rather than of recessive 
segregation. The problem of white in cattle is far from a complete 
solution. 
Red in cattle varies from a very dark red to light yellowish red. In 
the early days of the Shorthorn breed all these shades were represented 
but now the very dark reds and the yellowish reds are looked upon with 
disfavor. There is a little evidence of sharp segregation between some 
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