The following is an excerpt from "Accelerated C++":
"Derived objects are constructed by:
1. Allocating space for the entire object (base class members as well as derived class members);
2. Calling the base-class constructor to initialize the base-class part of the object;
3. Initializing the members of the derived class as directed by the constructor initializer;
4. Executing the body of the derived-class constructor, if any."
Summarizing the answers and comments: Calling a constructor of the base class from a subclass' constructor body is impossible in the sense that #2 above must precede #4. But we still can create a base object in the derived constructor body thus calling a base constructor. It will be an object different from the object being constructed with the currently executed derived constructor.