It turns out that you use this very same syntax for member object initialization when using composition. For composition, you give the names of the objects instead of the class names. If you have more than one constructor call in the initializer list, you separate the calls with commas:

This is the beginning of a constructor for class MyType2, which is inherited from Bar and contains a member object called m. Note that while you can see the type of the base class in the constructor initializer list, you only see the member object identifier.