Yeah frogs are cool because they go through, I guess you could call it, a visable embryonic-like set of changes (tadpole to adult). I can hypothesize why an injury would cause this... in a nut shell, cells rely on/communicate with neighboring cells via receptors/ligands (cell-cell signalling) and also local hormone production (paracrine signalling) where the effect is on the cells near by...(this is different than say, testosterone, runs through your whole body and has diff effects at different sites.) So I'm thinking, when the frogs were injured, this communication broke down, cells "on the cut" no longer received signal saying "stay as skin" and began forming "leg cells" just as the "normal to-be-leg cells" would be lacking this signal. A lot of this stuff requires concentration gradients etc of hormones and depending on how much hormone is present, the cell will be determined to a different fate.
Now that I think about it, I think gonads (like the fish in this example) is determined by the Y chromosome. Basically, if you have XX, youre the default and will always develop ovaries. Whereas in males you have XY, and the Y chromosome has genes to develop testes. I'm running into a wall now on how hermaphroditic events occur...blah I'll get back to you once I finish my reproduction block.
Oh btw, in my other post the example of where "the offspring would inherit faulty DNA replication machinery" would likely die far before being born. I just added it for completeness.
Wow, I've really hijacked this thread.