148 CONCLUSION [ch. 



On this view the various colour patterns found among 

 butterflies depend primarily upon definite hereditary 

 factors of which the number is by no means enormous. 

 Many of these factors are common to several or many 

 different groups, and a similar aggregate of colour 

 factors, whether in an Ithomiine, a Pierid, or a Papiho, 

 results in a similar colour scheme. The likeness may 

 be close without being exact because the total effect is 

 dependent in some degree on the size and relative 

 frequency of the scales and other structural features. 

 In so far as pattern goes Hypolimnas dvhius and 

 Amauris echeria (PI. VIII, figs. 7 and 8) are exceed- 

 ingly close. But inspection at once reveals a difference 

 in the quality of the scahng, giving to the Hypolimnas, 

 where the black and yellow meet, a softness or even 

 raggedness of outHne, which is distinct from the sharper 

 and more clear-cut borders of the Amauris. It is not 

 unreasonable to suppose that these species carry 

 identical factors for colour pattern, and that the 

 differences by which the eye distinguishes them are 

 dependent upon the minuter structural differences such 

 as occur in the scaling. So the eye would distinguish 

 between a pattern printed in identical coloiars on a 

 piece of cretonne and a piece of glazed calico. Though 

 pattern and colour were the same the difference in 

 material would yield a somewhat different effect. 



On the view suggested the occurrence of mimetic 

 resemblances is the expression of the fact that colour 

 pattern is dependent upon definite hereditary factors 

 of which the total number is by no means very great, 



