static class member of class's own type

Possible Duplicate:
Do static members of a class occupy memory if no object of that class is created?
Memory Allocation of Static Members in a Class

"A class is not considered defined untill its class body is complete, a class can not have data members of its own type. A class can have data members that are pointers/reference to its own type."

• C++ Primer (Lippman Lajoie)

Makes sense.

But why is this allowed then ?

class justAClass
{
     public  : 
     justAClass();

     private :          
     static justAClass justAMember;
}

For pointers it is understandable. But how will this above thing work ? How will i ever decide the size for object of such a class ? Isnt it a recursive case (with no base condition) to have a member of its own type, even if it is static ?