[Zope] Product Question

Hi all, have been experimenting with Products of late, I have a directory: FOO and in it. __init__.py with the correct defintion for initialize() and foo,py with a Product Interface and Implementation a la book. but I forgot one thing, a line that says : InitializeClass(MyProduct) Now, my product works fine <u>without</u> this line, and as I'm a curious sort, was wonderiing if anyone could tell me why if you have got initialze() in __jnit__.py why one would <i>need</i> to InitializeClass() in Product.py?? tia Matt