Page - 109 - in The Origin of Species

ON THE INTERCROSSING OF INDIVIDUALS 109 bees were to become rare in any country, it might be a great advantage to the plant to have a shorter or more deeply di- vided 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 structure mutually fa- vourable to each other. I am well aware that this doctrine of natural selection, 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 modern 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 insignifi- cant, when used in explaining the excavation of the deepest valleys or the formation of long lines of inland cliffs. Nat- ural selection acts only by the preservation and accumulation of small inherited modifications, each profitable to the pre- served being; and as modern geology has almost banished such views as the excavation of a great valley by a single diluvial 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 obvi- ous that two individuals must always (with the exception of the curious and not well understood cases of parthenogene- sis) unite for each birth; but in the case of hermaphrodites this is far from obvious. Nevertheless there is reason to be- lieve that with all hermaphrodites two individuals, either occasionally or habitually, concur for the reproduction of their kind. This view was long ago doubtfully suggested by Sprengel, Knight and Kolreutcr. We shall presently sec its importance ; but I must here treat the subject with extreme brevity, though I have the materials prepared for an ample discussion. All vertebrate animals, all insects, and some