Here's a little morsel that might save someone a bit of trouble.
C++ objects can have sub-objects ("has-a") and parent classes ("is-a"). This morsel doesn't concern itself with the parent class's objects but rather the encapsulated sub-objects defined by our very class. These encapsulated sub-objects can be initialized at construction time by an initializer list. Any objects that aren't initialized there you should initialize in the constructor itself, but it's preferred to do them in the initializer list if possible (for a variety of reasons including performance and code cleanliness).