"Throughout the long battle for the acceptance of his views, Darwin was plagued continually by his inability to compress the scale of nature to demonstrate a transformation of species to his critics. Had he known it, an example was at hand which would have provided him with the proof he needed. The case was an exceedingly rare one, in which a major evolutionary change occurred in the brief interval of fifty years. The animal which underwent the transformation was a member of the insect world, the humble Peppered Moth, found in abundance throughout England."
January 1, 1970
https://en.wikiquote.org/wiki/Charles_Darwin