A flea has smaller fleas to prey on them, and these have smaller still to bite them, and so proceed ad infinitum.
A flea has smaller fleas to prey on them, and these have smaller still to bite them, and so proceed ad infinitum.
一只跳蚤有更小的跳蚤咬它，而后者有更小的咬它们，如此以至无穷。