Much of Darwin's later writing was on earthworms. Very few people read it, as it was quite difficult to get them to stop wriggling for long enough to read the words. Darwin could only fit a couple of words on each worm, so potential readers had to go to the book shop with a wheelbarrow, to bring a cubic metre of worms home. On the journey home, the worms would, rather inconsiderately, re-arrange themselves, meaning that it could take a good hour to find two consecutive worms, and the best part of a fortnight to read a sentence.
Reviewers widely agreed that they preferred his work on finches.