[Zope] Not persistent on all classes please

I have a class in a product, which inherits from another product which in turn inherits from another product class. Consequently, I have inherited from the persistance class which makes object stick in the ZODB after you close it down. Now that's nice and all and there's not much I can do about it. But suppose that in this particular subclass I do NOT want the persistance base class. I don't want these objects to stick in the ZODB. Is that possible to cicumvent? I would like to do something like this: class Subsubsubclass(basecomponent, - persistance) Peter PS. All I know about persistance is that if you base class it, you automatically get persistent objects. How it happens, I don't know.