“Still you might discover, in some roundabout way. Write to them, under an assumed name of course, for subscriptions to one or other cause⁠—or, better still, send a stamped typewritten reply postcard, with a request for a declaration for or against vivisection; people who would hesitate to commit themselves to a subscription will cheerfully write Yes or No on a prepaid postcard. If you can’t manage it that way, try and meet them at someone’s house and get into argument on the subject. I think Milly occasionally has one or other of them at her at-homes; you might have the luck to meet both of them there the same evening. Only it must be done soon. My invitations ought to go out by Wednesday or Thursday at the latest, and today is Friday.