So it looks like not only is Banshee derived from Logan. But Magneto and Charles discovered it and wiped Logan's memory of the whole period. AND, when Charles first used it it gave him exact duplicates of Logan's abilities. That is, if Logan's abilities are his abilities at all. At this point I wouldnt be surprised to learn that Wolverine's true mutant ability (being the first and all) was to create or catalyse benevolent mutations depending on the external stimulus that switches on the x-gene (In Charles' case of exhibiting Wolverine powers, the external stimulus was of a jungle environment and a brutal fight with a clawed and savage reptile). Logan's feral abilities are just a stabilisation of this power in his own body.