so GERMINAL SELECTION. 



tion similar slight deviations of the corresponding 

 character, — in this case the color, — ^just as slight 

 changes in the atomic composition of a molecule may 

 result in bestowing upon the latter widely different 

 properties. As soon, however, as the beginning has' 

 been made and a definite direction has been imparted 

 to the variation, as the result of this or that primary 

 variation's being* preferred, the selective process must 

 continue until the highest degree of faithfulness re- 

 quired by the species in the imitation of fresh leaves 

 has been attained. 



That the foregoing process has actually taken place 

 is evidenced not only by the presence of the beginnings 

 of such transformations, as found for example in some 

 greenish-tinted specimens of Kallima, but mainly by 

 certain species of the South American genus Cato^ 

 nephele, all of which are forest-butterflies, and which, 

 with many species having dark-brown under surfaces, 

 present some also with bright green under surfaces^ 

 a green that is not like the fresh green of our beech 

 and oak trees, but resembles the bright under surface 

 of the cherry-laurel leaf, and is the color of the under 

 surfaces of the thick, leathery leaves, colored dark- 

 green above, borne by many trees in the tropics. 



The difference between this and the old conception 

 of the selection-process consists not only in the fact 

 that a large number of individuals with the initial 

 stages of the desired variation is present from the 

 beginning, for always innumerable plus and minus 

 variations exist, but principally in the circumstance 

 that the constant uninterrupted prc^ess of the proc- 

 ess after it is once begun is assured, that there can 

 never be a lack of progressively advantageous varia- 

 tions in a large number of individuals. Selection, 



