Tests of Montrose's sagacity were constantly being devised, but there was some uncertainty about the interpretation of the resultant data since the twins were always ready to return to first principles and discuss whether cooperation with the human race was a sign of intelligence at all. Montrose had one undoubted talent, which was that he could at will make his sleek hair stand up on end, and transform himself from a smooth stripey cube into a fluffy sphere. This was called'Montrose's bird look'. 'Don't ask me where they get the money from,' said Casie. 'It's enough to make a Socialist of you.' 'But you are a Socialist, Casie,' said Mary. So were they all, of course, but this seemed notable only in the instance of Casie. 'I didn't say I wasn't, did I? I just said it was enough to make you one.' 'Do you know which is the largest of all birds?' said Edward, pushing his way in between Mary and his sister. 'No. Which is?» 'The cassowary. He eats Papuans. He kills them by hitting them with his feet.' 'I think the condor is bigger,' said Henrietta. 'It depends whether you mean wing-span or weight,' said Edward. 'What about the albatross?' said Paula. She was always ready to enter into an argument with her children, whom she treated invariably as rational adults. 'He has the biggest wing-span,' said Edward, 'but he has a much smaller body. Do you know how big a breast bone we should need to have if we were going to fly? Mary, do you know how big a breast bone we should need to have if we were going to fly?' 'I don't know,' said Mary. 'How big?' 'Fourteen feet wide.' 'Really? Fancy that.' 'In the case of the condor – 'said Paula.