I thought it was profound how he said that Darwin himself left his thesis open for rejection, being more virtuous that his followers. The idea that the bacterium motor has to exist with all parts and no gradual building of the parts would allow it to exist, is another strong argument, in a line of many similar cases, that gradual modification would in fact not allow life to continue. Gaps in development have not been filled in but as more fossil evidence is found only brings more gaps.