Creating class having reference to another class-object

For better understanding purpose I am trying to create class which have reference to another class-object, passing over constructor, and access its properties/methods. I've made simple example, it works as expected, but I am not sure this is proper (and best) way to do such things. Can you please review/criticize?

Code is below. Thank you in advance...

Sketch:

#include "MyClasses.h"

MyClass1 cl1(5);   //create object of MyClass1
MyClass2 cl2(&cl1); //create object of MyClass2

void setup() 
{
  delay(100);
  Serial.begin(115200);
  Serial.println();
  Serial.print("cl1 property: "); Serial.println( cl1.getProp() );
  Serial.print("cl2 internal property: "); Serial.println( cl2.getInternalProp() );
}

void loop() 
{

}

MyClasses.h:

#ifndef MyClasses_h
#define MyClasses_h
class MyClass1
{
  public:
    MyClass1(int a); //MyClass1 constructor
	int getProp();
  protected:
    int _a;
};

class MyClass2
{
  public:
    MyClass2(MyClass1* c); //MyClass2 constructor
	int getInternalProp();
  protected:
    MyClass1* _c;
};
#endif

MyClasses.cpp

#include "MyClasses.h"
MyClass1::MyClass1(int a)
{
  //MyClass1 constructor
  _a = a;
}

int MyClass1::getProp()
{
  return _a;
}

MyClass2::MyClass2(MyClass1* c)
{
  //MyClass2 constructor
  _c = c;
}

int MyClass2::getInternalProp()
{
  return _c->getProp();
}

Looks right !

How to modify MyClass2 to call its constructor as MyClass2 cl2(cl1), not as MyClass2 cl2(&cl1)?