No. 546] 1XCOXSTAXCY OF I 'XI T-( If ABAC TKHS 



858 



the question was raised whether tliey are or are not con- 

 stant. 



In our descriptions we call these characters A, Ti, C, 

 etc., and the recombinations are AB, BC, AC, etc. In 

 our formulae A is always A, and B is always B, but it is 

 an open question whether in our living animals the char- 

 acteristics or qualities designated by these symbols are 

 from generation to generation as constant and change- 

 less as the symbols. Bateson and Johannsen and Jen- 

 nings have assumed that they are, that a horn is always 

 a horn, and a toe a toe. When it is pointed out that 

 horns are not all alike, that they differ in size, shape and 

 color, the reply is made that these differences are due to 

 other things, that is, that these are independent qualities 

 not inherent in the horn itself. Now there is force in this 

 argument because we know that a particular color can be 

 dissociated from the horn, why not also size and shape? 

 Nevertheless if we dissociate from the horn all color, 

 size and shape we shall have no horn left. The real unit- 

 characters, therefore, which we can think of in a con- 

 crete way and deal with in actual breeding operations are 

 differences in degree of horn-development, in length, 

 thickness, curvature or coloration. Who shall say 

 whether these differences are few or many ? We can con- 

 ceive of an infinite number of gradations in size, shape 

 and color between known extremes and it is difficult to 

 believe that any one of these is impossible of realization. 

 Nevertheless an important body of present-day natural- 

 ists, those who with De Vries believe in mutation, would 

 have us think that these minor gradations are not herit- 

 able. Their reasoning is as follows. Suppose we cross 

 horned with hornless cattle. All the immediate offspring 

 are hornless, and the grandchildren 3 hornless to 1 

 horned. The horned grandchildren breed true. No 

 intermediates occur. Clearly one unit-character differ- 

 ence exists between horns and no horns. Therefore no 

 stable intermediate class can exist unless this unit-char- 

 acter changes. This they consider to be impossible. If 

 we call attention to a short-horned race as evidence 



