How to declare a virtual member (not a function) in a class

[Adnan]

I have a base class that has a couple of constant member 
variables. These variables are abstract, they will only get 
defined when the derived class gets constructed.

class Person {
     const string name;
     const int id;
}

class Male : Person {
     this(string name = "Unnamed Male") {
         static int nextID = 0;
         this.id = nextID++;
         this.name = name;
     }
}

The compiler restricts me from assigning those two functions. How 
can I get around this?