266 THE CROSSING, &C, 



tility " attends, degree for degree, the union, in any indi- 

 vidual, of the peculiar characters of any two or more 

 of these varieties, it becomes a strong argument in 

 favor of there being but one normal type for the 

 species Pigeon ; and, becomes a strong argument, also, 

 in favor of the view, — so strongly confirmed by the 

 phenomena of close-interbreeding, — that any modifica- 

 tions of that type, such as are implied by the many 

 great and positive differences between such varieties, 

 work evil- to the constitutions, and to the reproductive 

 systems of the individuals. When Darwin had united, 

 in one bird, five distinct varieties, he had, before his 

 eyes, the closest approximation to the perfect type of 

 the Pigeon, which he had ever beheld. Had he ex- 

 perimented further, with that bird, he would have 

 found that its offspring could withstand, what no other 

 Pigeons could possibly suffer, viz., long-continued 

 close-interbreeding, for generation after generation, in 

 the nearest degree of relationship, and without any, or 

 with very little, evil effects wrought upon the constitu- 

 tion, or reproductive system. 



Again, on pages 247-8, he cites as a " fact," that : 



"All the races, though differing in many important 

 points of structure, produce perfectly fertile offspring ; 

 whilst, all the hybrids which have been produced 

 between even closely allied species, in the Pigeon 

 family, are sterile." 



It is, because the races do differ "in many im- 

 portant points of structure," that their mongrels are 

 "perfectly fertile." Physiology demands, that all of 

 those "many important points of structure," be com- 



