CROSSING AND CLOSE-INTERBREEDING. 221 



Herbert Spencer attributes the differences in the 

 effects to likeness, and to unlikeness, per se ; and, it is 

 amusing to note the pretentiously philosophical manner 

 in which he gives back to his readers, as an explana- 

 tion, the very facts which he essayed to explain for 



Individuals, realizing the 'perfect type, will be abso- 

 lutely alike; yet, they are the very individuals which 

 are exempt from any evil, from any degree of close- 

 interbreeding; whereas, if they interbreed with indi- 

 viduals unlike themselves, their offspring will be of 

 lessened fertility, and of lessened vigor; because, such 

 unlike individuals will necessarily be defective in some 

 • character, in order to be unlike those of the perfect type. 



It is not mere unlikeness; it is unlikeness of defect, 

 which abates, or precludes the evil effects; and it is not 

 mere likeness, but. likeness of defects, which causes or, 

 rather, aggravates, the evil. Where two animals are 

 deficient in the same endowments of their species, there 

 is no or little chance of repairing those portions of the 

 organism's balance; but, rather, an almost inevitable 

 necessity of augmenting those faults, in the offspring. 

 When, however, they are dissimilarly defective, there 

 is a strong probability, that the faults of either will be 

 remedied, in the offspring, by positive, corresponding 

 features in the other. Defects in each, or some defects 

 in each, will be supplied by an excellence which the 

 other derives, perhaps, from an ancestor, not common 

 to the former. 



Darwin says (p. 84, Vol. ii): 



"Certain individuals are prepotent, in transmitting 



