It is always permissible to ask a hostess if you may "bring" a dancing man who is a stranger to her. It is rather difficult to ask for an invitation for an extra girl, and still more difficult to ask for older people, because the hostess has no ground on which she can refuse without being rude; she can't say there is no room since no dance is really limited, and least of all a ball. Men who dance are always an asset, and the more the better; but a strange young girl hung around the neck of the hostess is about as welcome as a fog at a garden party. If the girl is to be brought and "looked after" by the lady asking for the invitation--who has herself been already invited--that is another matter, and the hostess can not well object. Or if the young girl is the fiancée of the man whose mother asks for the invitation, that is all right too; since he will undoubtedly come with her and see that she is not left alone. Invitations for older people are never asked for unless they are rather distinguished strangers and unquestionably suitable.
Invitations are never asked for persons whom the hostess already knows, since if she had cared to invite them she would have done so. It is, however, not at all out of the way for an intimate friend to remind her of some one who in receiving no invitation has more than likely been overlooked. If the omission was intentional, nothing need be said; if it was an oversight, the hostess is very glad to repair her forgetfulness.
An invitation that has been asked for a stranger is sent direct and without comment. For instance, when the Greatlakes of Chicago came to New York for a few weeks, Mrs. Norman asked both Mrs. Worldly and Mrs. Gilding to send them invitations; one to a musicale and the other to a ball. The Greatlakes received these invitations without Mrs. Norman's card enclosed or any other word of explanation, as it was taken for granted that Mrs. Norman would tell the Greatlakes that it was through her that the invitations were sent. The Greatlakes said "Thank you very much for asking us" when they bid their hostess good night, and they also left their cards immediately on the Worldlys and Gildings after the parties--but it was also the duty of Mrs. Norman to thank both hostesses--verbally--for sending the invitations.