I want to know the answer to the following question:
What did Darwin use to illustrate the way that original species change and adapt into new ones?
All the background I'm provided with is that "Natural selection was expected to work very slowly in forming new species, but given the effectiveness of artificial selection, he could "see no limit to the amount of change, to the beauty and infinite complexity of the coadaptations between all organic beings, one with another and with their physical conditions of life, which may be effected in the long course of time by nature's power of selection".". Is that enough to answer the question?