C++ create a usable method in the child class

This my base class

class Base {
protected:
    int number;
public:
    Base(int num);
    virtual void display() = 0;  
};

these two classes have inherited Base.

class Derived: public Base {
public:
    Derived(int num);
    void display(){cout <<"hello";}
    void other();
};

class Derived2: public Base {
public:
    Derived(int num);
    void display(){cout <<"hello other";}
};

this class allows me to just instantiate my two classes Derived and Derived2

class Foo{
private:
    Base * toto[2];
public:
    Foo(){
     toto[0] = new Derived;
     toto[1] = new Derived2;
    }

    void doSomething();
}

and I want to do this

void Foo::doSomething(){
    toto[0]->other();
}

thank's.