176 THE GENESIS OF SPECIES. 



thing to Natural Selection. It assumes, what must be 

 allowed, that ^ 7 ariations occur. In obedience to what 

 laws those variations themselves are produced is an 

 interesting speculation, and a most important subject 

 of inquiry. That such, laws or conditions of Variation 

 exist no one can doubt, unless he has been seduced by 

 Ovidian metamorphoses to believe in trees bleeding 

 human blood and human foreheads branching with the 

 antlers of the stag. A knowledge of those conditions 

 might fully explain the coexistence of similar structures 

 of diverse origin, consistently with the principle of 

 Natural Selection. The ignorance of them is scarcely a 

 proof that such coexistence does not harmonize with it. 



The objection that giraffes, which profited by long 

 necks in a time of drought, would find them a dis- 

 advantage subsequently, as requiring a greatly increased 

 size and strength of muscles to support them, overlooks 

 the law of correlation, by assuming that the elongated 

 neck would be out of proportion to the other conditions 

 of the creature's fabric. 



Mr. Mivart's fourth objection seems at least an ex- 

 tremely improbable opinion. He refers to Mr. Darwin's 

 expression, that the goose appears to have a highly in- 

 flexible organization, as if he himself thought it possible 

 for a species at length to attain to an organization com- 

 pletely inflexible. Such a view would imply two parents 

 exactly like one another, producing offspring exactly 

 like themselves ; and of such exact likenesses no known 

 families afford examples. 



