multiple inheritance

[Ginger Booth]

Hi, gang,

    I'm presently playing with variants of my base classes, and getting kinda
grumpy....  Time after time, I get into situations where I want to combine
two complexes of behaviors, like:

       SpeciesCommon       ParameterizedCommon
            |      \       /
            v       ---v---
  CompositeSpecies     ParameterizedSpecies
  
And yes, I'm used to C++. ;)  And yes, the "paste" button makes me profoundly
uneasy.

Is there a thought process I might acquire to become less aggravated at the
lack of multiple inheritance?  Does one just stack them up and paste bandages
over the parts that don't belong in the object under construction?  Can 
protocols have code?

Any Obj-C pointers appreciated.

Thanks,
    Ginger