protected void mismatch()
	{
		// first test: are we long enough?
		if ( pathLen >= MUM.MIN_LEN )
		{
			// second test: are we unique in the suffix tree?
			if ( pos.node.isLeaf() )
			{
				// third test
				if ( isMaximal() )		
				{
					addToPath( arc );
					// if we matched at least one byte of the current arc
					mum.update( start, offset, versions, 
						pos.edgePos-pathLen, pathLen, travelled );
				}
				// else it's a substring of the maximum match
			}
			// else it can't be a unique match
		}
		// else it's a tiddler: throw it back!
	}