Inherited function call from Base initializer :)

I ran into an interesting problem trying to create a default thread handler. Take a look at the code, because it's easier to explain that way :). I want the new Foo initializer to call the foo instance handler, not the Bar handler. Any ideas? Thanks >;-)

#include <iostream>

class Bar;
void callback( Bar *);

class Bar {
public:
	Bar( void) {
		callback( this);
	}
	
	virtual void instance( void) {
		std::cout << "Bar::instance was called" << std::endl;
	}
};

class Foo : public Bar {
	void instance( void) {
		std::cout << "Foo:instance was called" << std::endl;
	}
};

void callback( Bar *t) {
	t->instance();
}

int main( void) {
	new Foo();

	return 0;
}