Because damage remains marked on a creature until it's removed as the turn ends, nonlethal damage dealt to Experiment One may become lethal if you remove +1/+1 counters from it during that turn. In this case, it dies before the activated ability that would regenerate it resolves.
Experiment One
When comparing the stats as the evolve ability resolves, it's possible that the stat that's greater changes from power to toughness or vice versa. If this happens, the ability will still resolve and you'll put a +1/+1 counter on the creature with evolve. For example, if you control a 2/2 creature with evolve and a 1/3 creature enters the battlefield under your control, it toughness is greater so evolve will trigger. In response, the 1/3 creature gets +2/-2. When the evolve trigger tries to resolve, its power is greater. You'll put a +1/+1 counter on the creature with evolve.
If evolve triggers, the stat comparison will happen again when the ability tries to resolve. If neither stat of the new creature is greater, the ability will do nothing. If the creature that entered the battlefield leaves the battlefield before evolve tries to resolve, use its last known power and toughness to compare the stats.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Jack Wang
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
