Class Hierarchies – Ancestors and Descendants: In this book, I shall often talk about ‘descendant’ classes ‘inheriting’ features from their ‘ancestor’ classes. These terms deliberately suggest a kind a family re-lationship between ‘related’ classes. Each class in Ruby has only one parent. It may, however, descend from a long and distinguished fam-ily tree with many generations of parents, grandparents, great-grandparents and soon