My instances add instance-specific behavior to various class-describing objects in the system. This typically includes messages for initializing class variables and instance creation messages particular to a class. There is only one instance of a particular Metaclass, namely the class which is being described. A Metaclass shares the class variables of its instance. [Subtle] In general, the superclass hierarchy for metaclasses parallels that for classes. Thus, Integer superclass == Number, and Integer class superclass == Number class. However there is a singularity at Object. Here the class hierarchy terminates, but the metaclass hierarchy must wrap around to Class, since ALL metaclasses are subclasses of Class. Thus, Object superclass == nil, and Object class superclass == Class.