How do I make a blend follow neatly inside a curved object? E.G. I want to blend a banana object from black at one end to white at the other. So far, I've drawn the banana, filled it black and imposed a small ball filled white inside it at one end. I select both and do an option>command>B. It makes a beautiful blend but cuts across the hollow side of the banana and no amount of manipulation will contain it within the banana object. I think the problem has something to do with the 'spine' but trying to curve the spine just results in all shapes going wonky. I see a menu option to 'replace spine' but it remains ghosted under all conditions i.e., it can't be used and in any case I don't know exactly what it does. ???