212 CROSSING AND CLOSE-INTERBREEDING. 



which, is intimated the existence of some other, and 

 true law, which, while rendering explicable all the 

 many variations in the quantity of the effects, and the 

 frequent absence of all such effects, will show close- 

 interbreeding to be but a mere condition. 



Infinitely varied as are the facts of crossing, and of 

 close-interbreeding, they are susceptible of easy and 

 simple resolution, when the fact is recognized, that 

 want of integrity of structure, in the individuals of 

 any species, entails, in proportion, a want of physio- 

 logical integrity; and, that, when such want of in- 

 tegrity of structure is repaired (as it is in crossing, 

 through each parent contributing to the offspring, a 

 positive character which the other parent lacks), a pro- 

 portionate return to physiological integrity, is secured. 



Upon this principle, every one, without exception, 

 of the various perturbations, to which the reproductive 

 elements are observed to be subject, becomes per- 

 fectly explicable, and susceptible of both qualitative 

 and quantitative prevision. This explanation accords, 

 most rigorously, with each and every one of Darwin's 

 tens of thousands of facts, — whether of sexual, or of 

 asexual reproduction. Each one, of the thousands of 

 individuals of each species, will, when questioned, by 

 means of this rule, respond, and give the degree of its 

 departure from the original, perfect type of its species. 

 The evil effects of close-interbreeding, are faithful indi- 

 cations of the degree of such departure; and, the in- 

 crease of good from crossing, is an indication of the 

 degree of return, which has been made towards such 

 type. By this rule, moreover, the different data, — 



