In Time Machine by Wells, who are the Morlocks?

In the year 802,701 AD, the Time Traveller discovers that humans have evolved into two separate species:

• The Eloi — beautiful, childlike, weak surface dwellers who live above ground. They spend their days playing, eating fruit, and enjoying a seemingly peaceful existence.
• The Morlocks — pale, ape-like, underground-dwelling creatures who maintain the machinery that keeps the world running.

The twist is that the Morlocks are not simply monsters; they are the result of class division taken to an extreme.