little joke about advice to young girls.

There was no reason in the world why she should be The Girl. There were
fifteen or twenty of them in the class along with about as many men.
And, partly because there was no reason for his paying any special
attention to her, it annoyed him frightfully that he did.

She was good-looking, of course--a rather boyishly splendid young
creature of somewhere about twenty, with a heap of hair that had, in
spite of its rather commonplace chestnut color, a sort of electric
vitality about it. She was slightly prognathous, which gave a humorous
lift to her otherwise sensible nose. She had good straight-looking,
expressive eyes, too, and a big, wide, really beautiful mouth, with
square white teeth in it, which, when she smiled or yawned--and she
yawned more luxuriously than any girl who had ever sat in his
classes--exerted a sort of hypnotic effect on him. All that, however,
left unexplained the quality she had of making you, whatever she did,
irresistibly aware of her. And, conversely, unaware of every one else
about her. A bit of campus slang occurred to him as quite literally
applicable to her. She had all the rest of them faded.

It wasn't, apparently, an effect she tried for. He had to acquit her of
that. Not even, perhaps, one that she was conscious of. When she came
early to one of his lectures--it didn't happen often--the men, showed a
practical unanimity in trying to choose seats near by, or at least where
they could see her. But while this didn't distress her at all--they were
welcome to look if they liked--she struck no attitudes for their
benefit. A sort of breezy indifference--he selected that phrase finally
as the best description of her attitude toward all of them, including
himself. When she was late, as she usually was, she slid