Preface to the English Edition. xxi 



these markings might have been that they were 

 to be regarded as ornaments, but this view pre- 

 cludes the possibility of referring them either to 

 Natural Selection or to the influence of direct 

 changes in the environment. 



The markings of caterpillars offered also 

 another advantage which cannot be lightly 

 estimated ; they precluded from the first any 

 attempt at an explanation by means of Sexual 

 Selection. Although I am strongly convinced of 

 the activity and great importance of this last 

 process of selection, its effects cannot be esti- 

 mated in any particular case, and the origin of a 

 cycle of forms could never be clearly traced to its 

 various factors, if Sexual Selection had also to be 

 taken into consideration. Thus, we may fairly 

 suppose that many features in the markings of 

 butterflies owe their origin to Sexual Selection, 

 but we are, at least at present, quite in the dark 

 as to how many and which of these characters 

 can be traced to this factor. 



An investigation such as that which has been 

 kept in view in this second essay would have been 

 impracticable in the case of butterflies, as well as 

 in the analogous case of the colouring and marking 

 of birds, because it would have always been 

 doubtful whether a character which did not 

 appear to be attributable to any of the other 

 transforming factors, should not be referred to 

 Sexual Selection. It would have been impossible 



b 



