THE INTRODUCED SPARROW. 1 1 



established as phylogenic ? Is the mechanism of heredity 

 affected immediately, through the action of the new environ- 

 ment on the germ itself, or mediately, through the influence of 

 ontogenic somatic change ? 



I think it improbable that the new form adopted by the 

 American egg can be the result of the selection of adaptive 

 fortuitous variations. 



Fortuitous variation means chance-variation, and, although it 

 is mathematically possible for the same particular variation to 

 appear fortuitously in all or nearly all of the American eggs, it 

 is absurd for us to suppose that this has actually happened. We 

 cannot believe that the new form and shape, which are so uni- 

 versally presented by the American species, are variations 

 which have arisen by mere chance. Again, even admitting 

 for the sake of argument that a chance- variation has simultane- 

 ously appeared in nearly all the American individuals, what 

 have we to show that this variation is adaptive, that it has 

 selective value ? Who will say that the shorter egg is a supe- 

 rior egg, or that the more spherical egg is, in the new environ- 

 ment, an improvement on the European type ? 



In the third place, even admitting the all-sufficiency of natural 

 selection, there has not been sufficient time for the establish- 

 ment of a new type of egg, that is, for the conclusion of the 

 struggle between " Nature and Nurture." Neo-Darwinians deal 

 with centuries and ages. Forty years can accomplish nothing. 



If we again refer to the curves, we shall find other reasons 

 for the belief that the American type of egg is not to be 

 explained by the principle of adaptive fortuity. 



Although the American eggs are unquestionably more vari- 

 able, as is shown by the more elongated base lines, the curves 

 rising to the culminating points of American variation are no 

 less regular than those rising to the culminating points of 

 British variation. This means that the new type is definitely 

 established and that nearly all the eggs tend towards this type. 

 Now, is it likely that mere chance-variation would yield an 

 American curve so nearly parallel to the British curve ? If the 

 selection favors those eggs which are located on ordinates 21 

 and 73 (Diagrams I and II), that is, favors a certain type, why 



