SEVENTH ANNUAL YEAR BOOK-PART VI. 253 



to be understood that this is not mere theory, but has been proved to hold 

 true in so many instances, both in the animal and the plant world, that 

 there can be no doubt about its correctness as a general principle. 



Dr. E. W. Gammon, of Sioux City, who is breeding polled Herefords 

 at St. Charles, Iowa, told me a few days ago that both he and his uncle, 

 Warren Gammon, the founder of the double standard polled Hereford 

 breed, have observed that their results in breeding coincide very closely, 

 indeed, with Mendel's law, and that they have found the law a great help 

 to them in determining whether or not certain polled animals were pure 

 polls or hybrids. I shall not recite more instances of this kind. Many 

 might be cited from the experience of both plant and animal breeders in 

 this country and abroad. Hays, Webber, Spillman and others in this 

 country have found the law useful and have repeatedly urged breeders to 

 become acquainted with it. 



Those familiar with the laws of breeding as they are understood today 

 know that there are exceptions to all of them. We say like produces like, 

 but we all know that this is only true within certain bounds and that it is 

 modified by laws of variation, atavism and correlation. Just as there are 

 deviations in the first law of breeding, like produces like, so are there 

 also deviations from Mendel's law of dominance, a fact that Mendel has 

 always recognized. For example, in some cases the crossbred offspring 

 acquires a character intermediate between those of either of its parents. 

 Examples of that kind were observed by Mendel in crossing peas of dif- 

 ferent height. Again a certain character of the offspring may be intensi- 

 fied, as for instance, according to Mendel's observations, when a brown 

 seeded variety of beans is crossed with a white seeded variety, the 

 offspring produced seeds of a darker brown than those of the brown 

 seeded parent. And still further, the offspring may acquire a character 

 entirely different from that of either parent. For example, a cross be- 

 tween black and white spotted and albino mice produces offspring gray 

 in color. Whether cases of that kind occur where a given character of 

 one parent is distinctly dominant remains, so far as I know, to be proved. 

 While, as indicated, the law of dominance does apparently not always 

 assert itself, and while no one can tell beforehand what the result of a 

 certain cross will be, if such a cross has never before been made, it should 

 be borne in mind that the law is, nevertheless, positive and uniform in 

 its action. If it has once been demonstrated what the result of a certain 

 cross is, we may reasonably expect the same results in succeeding similar 

 crosses. It has been said that an Augus bull is the greatest dehorner of 

 a herd of cattle ever known. This is equivalent to saying that the polled 

 character in Angus cattle, when they are crossed with horned cattle, is 

 dominant and that we may always, to give a concrete example, expect a 

 polled calf from a cross between a pure Angus poll and a Shorthorn cow. 



Mendel's law, while it has given us much valuable information, will in 

 no way change our methods of breeding. It does not change the laws 

 that have heretofore been our guides — it simply adds to them; it is 

 explanatory, so to speak, and enables us to understand and explain many 

 things that heretofore were inexplicable and often served to discourage 

 the breeder. It enables us to work with a definite idea in view and gives 

 us assurance that a certain result can be reached if the plan is well laid 



