> It's returning nil, but I find this is a bit strange, perhaps because of
> how I'm used to have things working in Objective-C (where only Object has
> nil as superclass). 

In Smalltalk, Object is the canonical root of the class hierarchy, but
you can have other roots, as well, typically for proxies.  BTW, you
can do this in Objective-C, also.

> Objective-C uses some sort of simplified form of what Squeak offers :
> there is no separate metaclass hierarchy. 

[snip of Objective-C hierarchy diagram & explaination]

As you head in the "meta" direction in Objective-C, it disolves
gradually from objects to the C structures that implement objects.

-- Mike