MfS CELL A NEO US. 119 



due in their inception to a regular law of progressive 

 modification ; and they have been fixed and stereo- 

 typed in each species by the selective action of the 

 proper beetles, bees, moths, or butterflies. Not only 

 can we say why such a colour, once happening to 

 appear, has been favoured in the struggle for exist- 

 ence, but also why that colour should ever make its 

 appearance in the first place, which is a condition 

 precedent to its being favoured or selected at all. 

 For example, blue pigments are often found in the 

 most highly-developed flowers, because blue pigments 

 are apparently a natural product of high modification 

 a simple chemical outcome of certain extremely 

 complex biological changes. On the other hand, 

 bees show a marked taste for blue, because blue is 

 the colour of the most advanced flowers ; and by 

 always selecting such, where possible, they both keep 

 up and sharpen their own taste, and at the same 

 time give additional opportunities to the blue flowers, 

 which thus ensure proper fertilisation. May we not 

 say that it ought always to be the object of naturalists 

 in this manner to show not only why such and such 

 a " spontaneous " variation should have been favoured 

 whenever it occurred, but also to show why and how 

 it could ever have occurred at all ? 



THE END. 



