118 ON THE INTBRCROSSINa [Chap. IV. 



in any country, it might be a great advantage to the 

 plant to have a shorter or more deeply divided corolla, so 

 that the hive-bees should be enabled to suck its flowers. 

 Thus I can understand how a flower and a bee might 

 slowly become, either simultaneously or one after the 

 other, modified and adapted to each other in the most 

 perfect manner, by the continued preservation of all the 

 individuals which presented slight deviations of struc- 

 ture mutually favourable to each other. 



I am well aware that this doctrine of natural selec- 

 tion, exemplified in the above imaginary instances, is 

 open to the same objections which were first urged 

 against Sir Charles Lyell's noble views on " the modem 

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

 now seldom hear the agencies which we see still at work, 

 spoken of as trifling or insignificant, when used in ex- 

 plaining the excavation of the deepest valleys or the for- 

 mation of long lines of inland cliffs. Natural selection 

 acts only by the preservation and accumulation of small 

 inherited modifications, each profitable to the preserved 

 being; and as modern geology has almost banished such 

 views as the excavation of a great valley by a single dilu- 

 vial wave, so will natural selection banish the belief of 

 the continued creation of new organic beings, or of any 

 great and sudden modification in their structure. 



On the Intercrossing of Individuals. 



I must here introduce a short digression. In the 

 case of animals and plants with separated sexes, it is of 

 course obvious that two individuals must always (with 

 the exception of the curious and not well understood 

 cases of parthenogenesis) unite for each birth; but in 



