Here's what it says:
The Legion origin story was first published in Giant Superboy #47 (G-47) - May-June, 1968. When we began to get material together for an all-Legion issue, we discovered that thre had never actually ben an origin dreamed up for that organization. So I got busy and wrote one.
There have been some drastic changes in the origin stories of the individual heroes, though, in the first Legion tale, which appeared in Adventure Comics #247 (April, 1958). Saturn Girl said, "The scientists of Saturn, who are experts in telepathy, taught me how to read minds and also cast my mental commands anywhere." Cosmic Boy thought, "Special serums gave me magnetic eyes of super-power." And Lightning Boy (not called Lightning Lad in the story) revealed, "My hands are like the positive and negative poles of a battery. Each time I clap them together, a super-lightning flash leaps forth."
In Superman #147 (August, 1961) (do you get the feeling that there are a lot of 47's connected with the Legion?), the adult Legion and the Legion of Super-Villains were introduced. In this one, Lightning Lord said that he and his brother, Lightning Man (formerly Lightning Lad), had gained their power while exploring some woods on the planet Korbal. A lightning monster had blasted them, transferring some of its power into them. By this time, Lightning Man was no long [sic] clapping his hands to get lightning, but Cosmic Man was still using his magnetic eyes.
He was using his hands, though, in Giant Superman Annual #4 (1961), when a special feature on the origins of the Legionnaires was published. Lightning Lad's origin was the one given in Superman: "Lightning Lad gained mastery of lightning when a blast from a lightning monster on the planet Korbal freakishly electrified his body." As for the others, "Cosmic Boy possesses the power of super-magnetism, which he inherited from his parents on the planet Braal. Evolution has given Braalians the power to magnetically battle metal monsters who roam their world." And "Saturn Girl comes from Saturn, where all people can perform amazing mental feats."
In Adventure #308 (May, 1963), after Lightning Lad was killed in action (he was later revived), his sister, Lightning Lass, impersonated him. Two versions of his origin were given. In one, he was in a space-flier that ran out of power, forcing him to land on Krobal. He tried to get the lightning monsters to shoot their bolts at it to recharge it, but instead, they aimed at him, from all sides. This neutralized the bolts, charging the youth with lightning power greater than theirs. (Absurdly, he was already wearing his lightning insignia in this origin.) Toward the end of this story, the scene was repeated, but with the addition of his sister. Not only was the early account by Lightning Lord ignored, but he himself was completely omitted!
I had added R.J. Brande in a story I wrote for Adventure #350. I did my best to tie together all the loose ends in writing the origin reprinted in this issue.