Before Oblonsky leaves, Anna's son Seryozha (now called Master Sergius or Sergei Alexeich) comes into the room.
Oblonsky remembers that Anna asked him to see the boy.
Karenin tells Oblonsky not to mention Anna. He says the boy was ill for a time after his mother's unexpected visit, but that going to school has been extremely beneficial for him.
The boy looks healthy, happy, and handsome, but he's not at all keen to talk to Oblonsky.
It's been a year since Seryozha saw his mother, and he's tamped down all the associated memories and emotions, considering them fit for girls, not boys. He resigns himself to the idea that he has to live with his father, and considers his sentiments for his mother to be shameful.
Thus, it's really unpleasant for Seryozha to see his uncle because Oblonsky resembles Anna, and it calls up those feelings for her that he now considers humiliating.
Seryozha tries to avoid his uncle, but Oblonsky follows Seryozha out of the room and makes idle conversation for a little bit. Finally Oblonsky can't help asking if Seryozha remembers his mother. Seryozha answers in the negative, blushing. Of course he remembers, but he doesn't want to talk about it.
Half an hour later, Seryozha's tutor finds him on the staircase. He was either crying or in a bad mood. Seryozha yells at the world, asking why it matters if he remembers his mother.