"Katerina Sergeyevna!" began Arkady suddenly. "It may be all the same to you but I should like you to know that I wouldn't exchange you for your sister or for any one else in the world either." (25.79)
Is Arkady confessing to love or admiration here? Why do you think he leaves out the word love? Why is it that the discussion of Anna Sergeyevna brings this out in him?