The rail is simply doubled and has no branches anywhere, for my brush has destroyed them all.

What will the caterpillars do on this deceptive, closed path?
Will they walk endlessly round and round until their strength gives out entirely?
The old schoolmen were fond of quoting Buridan's Ass, that famous Donkey who, when placed between two bundles of hay, starved to death because he was unable to decide in favour of either by breaking the equilibrium between two equal but opposite attractions.

They slandered the worthy animal.

The Ass, who is no more foolish than any one else, would reply to the logical snare by feasting off both bundles.

Will my caterpillars show a little of his mother wit?
Will they, after many attempts, be able to break the equilibrium of their closed circuit, which keeps them on a road without a turning?
Will they make up their minds to swerve to this side or that, which is the only method of reaching their bundle of hay, the green branch yonder, quite near, not two feet off?
I thought that they would and I was wrong.