42 THE BREEDING PROBLEM. 



From a long series of experiments on plants, given in my book On Vie Effects 

 of Gross and Self- Fertilization, the conclusion seems clear that there is no 

 mysterious evil in the mere fact of the nearest relations breeding together; 

 but that evil follows (independently of inherited disease or weakness) from 

 the circumstance of near relations generally possessing a closely similar con- 

 stitution. However little we may be able to explain the cause, the facts detailed 

 by me show that the male and female sexual elements must be dilTercntiated 

 to a certain degree, in order to unite properly, and to give birth to a vigorous 

 progeny. Such differentiation of the sexual elements follows from the parents 

 and their ancestors having lived some generations imder different conditions 

 of life. 



The closest interbreeding does not seem to Induce variability or a departure 

 from the typical form, of the race or family, but it causes loss of size, of con- 

 stitutional vigor in resisting unfavorable influences, and often of fertility. On 

 the other hand, a cross between plants of the same sub-variety, which have 

 been grown during some generations under different conditions, increases to 

 an extraordinary degree the size and vigor of the offspring. 



Some kinds of plants bear self-fertilization much better than others ; never- 

 theless it has been proved that these profit greatly by a cross with a fresh stock. 

 So it appears to be with animals, for Short-horn cattle — perhaps all cattle — 

 ■can withstand close interbreeding with very little injury ; but if they could 

 be crossed with a distinct stock without any loss of their excellent qualities, 

 it would be a most surprising fact if the oftspring did not also profit in a very 

 high degree in constitutional vigor. If, therefore, any one chose to risk 

 breeding from an animal which suflered from some inheritable disease or 

 weakness, he would act wisely to look out, not merely for a perfectly sound 

 animal of the other sex, but for one belonging to another strain, which had 

 been bred during several generations at a distant place, under as different con- 

 ditions as to soil, climate, etc., as possible, for in this case he might hope that 

 the offspring, by having gained in constitutional vigor, would be enabled to 

 throw oft' the taint in their blood. 



As it seems to be a law of nature, and particularly of animal 

 existence, that every organism carries within itself the seeds of 

 decay— the elements of decline — so the law of heredity looks con- 

 stantly in the direction of concentrating infirmity and hastening 

 dissolution. To counteract this, is part of the province of drawing 

 fresh supplies in the way of outcrossing, and the process of breeding 

 in this regard is a revival of the contest between the two forces of 

 conservatism and progression. But this same conservatism in nature 

 and in animal existence is a law of decline, and can only be success- 

 fully combated by a resort to the other, or laAV of progressive re- 

 enforcement. And the grand plane of successful breeding is reached 

 when the breeder shall at the same time and by the same processes 

 l)oth re-enforce the constitutional vigor and nervous energy of his 



