Parasitic worm species Donut proposes as the explanation for Tagg, before Mordecai rules it out.
Puzzling over how Epitome Tagg could be living inside Louis's new organs, Donut suggests in Warlord Chat that maybe he is a Valtay Worm.
Mordecai shuts the theory down: worms can't inhabit biomechanical organs, only biological brains. Rosetta agrees, noting that Gondii need wetware while Reavers can isolate processing anywhere in the body — leaving the cyborg explanation as the only one that fits.
Rejected hypothesis for Tagg's survival, eliminated in favor of the cyborg theory.