When Mr. Summers, who is in charge of running the annual lottery, asks for a member of the Watson family to come and draw a ticket, a tall boy steps forward. The boy says that he will be drawing the ticket for the Watson family this year. He seems to be nervous and is cheered on by members of the crowd. Indeed, from the crowd we hear one person shout, "Good fellow, Jack," and another shout, "Glad to see your mother's got a man to do it."
The implication here is that Mrs. Watson's husband is not present at this year's lottery because he won the lottery last year, and, like all supposed winners, was promptly stoned to death. This would explain why the crowd seems to be so sympathetic and so encouraging to the Watson boy. They appreciate that the boy has lost his father. They also appreciate that the boy must be rather anxious about taking his father's place this year, given that he saw what happened when his father drew the winning ticket last year.
When one of the crowd shouts out, "Glad to see your mother's got a man to do it," we might infer that this crowd member is glad that Mrs. Watson has found, in her son, a man to take the place of her husband. This in turn suggests that the husband was recently alive, compounding the impression that he was killed as the winner of the previous year's lottery.