To give his theory credence (or believability). twain claims that — (from mark twain's "the lowest animal")
he heard about it from a famous scientist
he read about it in scientific books and
drew his conclusions from his own experiments
it was created by charles darwin

The man thinks she's the lady he's trying to find. she then lifts the veil and he announces that he'd made a mistake and that he'd thought she was the woman, but had been wrong. truthfully, though, he'd been right. this reveals that the he didnt recognize her (though he said he would recognize her voice or her build) and that he's still looking for the girl. he doesnt find the woman appealing or attractive, and is more or less disgusted by her appearance. he didn't understand what the lady meant when she told him the story about her "friend"