Chap. IV. NATUEAL SELECTION. 95 



clover, which is visited by humble-bees alone ; so that 

 whole fields of the red clover offer in vain an abundant 

 supply of precious nectar to the hive-bee. Thus it 

 might be a great advantage to the hive-bee to have a 

 slightly longer or differently constructed proboscis. On 

 the other hand, I have found by experiment that the 

 fertility of clover greatly depends on bees visiting and 

 moving parts of the corolla, so as to push the pollen 

 on to the stigmatic surface. Hence, again, if humble- 

 bees were to become rare in any country, it might 

 be a great advantage to the red clover to have a 

 shorter or more deeply divided tube to its corolla, so 

 that the hive-bee could visit its flowers. Thus I can 

 understand how a flower and a bee might slowly be- 

 come, either simultaneously or one after the other, 

 modified and adapted in the most perfect manner to 

 each other, by the continued preservation of individuals 

 presenting mutual and slightly favourable deviations of 

 structure. 



I am well aware that this doctrine of natural selection, 

 exemplified in the above imaginary instances, is open to 

 the same objections which were at first urged against 

 Sir Charles Lyell's noble views on " the modern changes 

 of the earth, as illustrative of geology ;" but we now 

 very seldom hear the action, for instance, of the coast- 

 waves, called a trifling and insignificant cause, when 

 applied to the excavation of gigantic valleys or to the 

 formation of the longest lines of inland cliffs. Natural 

 selection can act only by the preservation and accumula- 

 tion of infinitesimally small inherited modifications, each 

 profitable to the preserved being ; and as modern 

 geology has almost banished such views as the excava- 

 tion of a great valley by a single diluvial wave, so 

 will natural selection, if it be a true principle, banish 

 the belief of the continued creation of new organic 



