200 Tin-: evolution theory 



of butteillios and iiu)ths wliit-li tly from flower to flower. Thus the 

 viola of the Higli Alps has become a ' butterfly-flower ' by the develop- 

 me)it of its nectaries into a long spur, accessil)le only to the proboscis 

 of a moth or butterfly. The chance which led certain individuals of 

 the ancestral species to climb the Alps must also have supplied the 

 incentive to the production of the changes adapted to the visits of 

 the prevalent insect. The hypothesis of a predestinating Power 

 of Development sufl'ers utter shipwreck in face of facts like these. 



We liave, furthermore, an excellent touchstone for the reality of 

 tlie processes of selection in the quality of the variations in flowers 

 and insects. Natural selection can only bring about those changes 

 which are of use to the possessors themselves; we should therefore 

 expect to find among flowers only such arrangements as are, directly or 

 indirectly, of use to them, and, conversely, among insects only such as 

 are useful to the insect. 



And this is what we actually do find. All the arrangements of 

 the flowers — their colour, their form, their honey-guides, their hairy 

 honey-paths (Iris), their fragrance, and their honey itself — are all 

 indirectly useful to the plant itself, because they all co-operate in 

 compelling the honey-seeking insect to effect the fertilization of the 

 flower. This is most clearly seen in the case of the so-called 

 ' Deceptive ' flowers, which attract insects b^^ their size and beauty, 

 their fragrance, and their resemblance to other flowers, and force 

 their visitors to be the means of their cross-fertilization, although 

 they contain no nectar at all. This is the case, according to Hermann 

 Mliller, with the most beautiful of our indigenous orchids, the lady's 

 slipper {Gypripediurn calceolaris). This flower is visited l)y bees of 

 the genus Andrena, which creep into the large wooden-shoe-shaped 

 under lip in the search for honey, only to find themselves prisoners, 

 for they cannot get out, at least by the way they came in, because of 

 the steep and smoothly polished walls of the flower. There is only 

 one way for the l)ee ; it must force itself under the stigma, which it 

 can only do with great exertion, and not without being smeared with 

 j)ollen, which it carries to the next flower into which it creeps. It 

 can only leave this one in the same way, and thus the pollen is trans- 

 ferred to the stigma by a mechanical necessity. 



Such remarkable cases remind us in some ways of those cases 

 of mimicry in which the deceptions have to be used with caution or 

 they lose their effect. One might be disposed to imagine that such 

 an intelligent insect as a bee would not be deceived by the lady's 

 slipper more than once, and would not creep into a second flower 

 after discovering that there was no nectar in the first. But this 



