inheritance from classes own members?

Reading about Inheritance I don't quite understand the following

Code:

---

Mammal::Mammal(): itsAge(1), itsWeight(5)
{
cout << "Mammal constructor...\n";
}

---

My question is, what is realy going on here? itsAge and itsWeight are both member variables of the Mammal class. Is this Inheritance and why would a class try to inherit from itself?

Can someone please explain?

Here.

Thanks that fully explains it, and thanks to Cat for the origional answer.

I had searched prior to posting but could only find inheritance from base classes and nothing such as this.