LECTURE LXXXI. 



INFLUENCE OF THE LAW OF VARIATION. 



The breeder of live stock notices from time to time 

 changes in his animals; the progeny do not always resemble 

 the parents in every particular. This difference in some in- 

 stances is very slight and confined to just a few points. In 

 other instances these changes are very marked; so marked 

 as to present an animal very different from either of the 

 parents. It is doubtful if there ever was an instance in 

 animal breeding in which the offspring did not in some way, 

 perhaps very little, differ from the parents. This being the 

 case, we can see that there is some law at work all the 

 time, which produces results different from the first law, that 

 of heredity, which is that like produces like. 



This new law is called the law of variation, and may be 

 defined as the law that like does not always produce like. 

 In a sense it is antagonistic to the law that like produces 

 like. Still they both seem to operate in animal breeding in 

 a useful manner. The first law might be more properly de- 

 fined by saying that like produces like in a general way. 

 This would allow of some minor points of difference which 

 are always present. It may be a slight difference of form, 

 in any one of its numerous details. It may be a difference in 

 temperament, in color, in function or in any one of a great 

 many other points which might be mentioned. This is one 

 of the most important and useful laws in animal breeding. 

 Without it, it would be impossible for us in any way to im- 

 prove our animals. It may act in the way of improvement 

 or in the way of deterioration or retrogression. It is to this 

 law that we owe the presence of so many different breeds 

 of live stock. It is through the influence of this law that 

 we are able to breed animals for special, definite purposes, 

 such as the ideal beef steer and the highly developed dairy 

 cow. They both represent variations from the original type. 

 It is through the influence and presence of this law that our 

 various breeds and types of animals retrogrades so rapidly 



