124 Evolution and Adaptation 



Or only a third, fifth, or tenth part of the individuals may 

 have been thus affected, of which fact several instances could 

 be given. Thus Graba estimates that about one-fifth of the 

 guillemots in the Faroe Islands consist of a variety so well 

 marked, that it was formerly ranked as a distinct species 

 under the name of Uria lacrymans. In cases of this kind, if 

 the variation were of a beneficial nature, the original form 

 would soon be supplanted by the modified form, through the 

 survival of the fittest." 



Do not the admissions in this paragraph almost amount to 

 a withdrawal of much that has preceded in regard to the 

 survival of fluctuating, individual differences ? In the last 

 edition, from which we have just quoted, Darwin, in response 

 to the criticisms which his book met, inserted here and there 

 statements that are in many ways in contradiction to the 

 statements in the first edition, and yet the earlier statements 

 have been allowed to stand for the most part. 



The next example is also worthy of careful examination, 

 since it appears to prove too much : — 



" It may be worth while to give another and more complex 

 illustration of the action of natural selection. Certain plants 

 excrete sweet juice, apparently for the sake of eliminating 

 something injurious from the sap : this is effected, for in- 

 stance, by glands at the base of the stipules in some Legu- 

 minosse, and at the backs of the leaves of the common laurel. 

 This juice, though small in quantity, is greedily sought by 

 insects ; but their visits do not in any way benefit the plant. 

 Now, let us suppose that the juice or nectar was excreted 

 from the inside of the flowers of a certain number of plants 

 of any species. Insects in seeking the nectar would get 

 dusted with pollen, and would often transport it from one 

 flower to another. The flowers of two distinct individuals of 

 the same species would thus get crossed; the act of crossing, 

 as can be fully proved, gives rise to vigorous seedlings, 

 which consequently would have the best chance of flourish- 



