of the form. The leaf-like form results from an acumina- 

 tion and elongation of the wings, which in turn results from 

 a marked elongation of the rim of the fore-wing. And this 

 again is produced by the proportionately greater growth of 

 one part of the wing-section than of the others. 



With reference to the reason of this growth it is of 

 importance to note that experiments, consisting in the ap- 

 plication of artificial heat to the chrysales of the swallow- 

 tail and sailor-butterfly, demonstrated that by this means 

 "the fore-wing is drawn out more toward the outer wing- 

 vein, and the rim of the fore-wing becomes more elongated 

 and curved." It is observed, however, that the natural 

 heat-forms of the same genera and species, namely, the 

 summer-forms and those which live in the warm southern 

 climate, exhibit, for instance, in the case of butterflies akin 

 to the sailor, the same features, the elongation and more 

 marked curvature of the fore-rim of the fore-wings and the 

 consequent more extended form, that are produced by the 

 action of artificial heat. Manifestly this is a matter of vital 

 importance for the solution of the question: heat, whether 

 artificial or natural, produces a difference in growth, which 

 results in a change of form and coloring. There is conse- 

 quently no room for natural selection or the struggle for 

 existence. 



The leaf-like form is generally associated with the 

 dark, faded colors of dry leaves, and when this similarity 

 disappears even bright colors appear on the fore-wings. In 

 many cases the resemblance to leaves is very imperfect; 



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