Yevamos, Chapter 9, Mishnah 6. This mishnah is similar in structure to the previous one: it too traces the stages of a woman who marries a kohen, a Levi or a Yisrael and bears them sons, and asks whether she may eat Terumah or ma'aser. The one significant difference is the starting point: the previous mishnah began with the daughter of a Yisrael and followed her through the various stages, whereas here the woman begins as the daughter of a kohen - and for that reason things unfold differently.
The stages of marriage in order:
"Bas kohen shenis'ah l'Yisrael - lo sochal biTerumah" - the daughter of a kohen, who had been eating Terumah by virtue of her father, is forbidden to eat Terumah once she marries a Yisrael, who is an outsider and not a kohen.
"Mes v'lah heimenu ben - lo sochal biTerumah" - even though her Yisrael husband died, as long as she has a son from him she does not eat Terumah. Only when she has no children from the Yisrael does she return to her father's house and eat Terumah.
"Nis'ah l'Levi - tochal b'ma'aser" - according to this Tanna, a Levi and his wife, and likewise a woman who has a son from a Levi, eat ma'aser. Therefore, once she marries a Levi, she eats ma'aser.
"Mes v'lah heimenu ben - tochal b'ma'aser" - even though the Levi died, by virtue of the son from him she continues to eat ma'aser.
"Nis'ah l'kohen - tochal biTerumah" - here she goes back to eating Terumah. Although she is the daughter of a kohen to begin with, she could not eat Terumah because of the marriages and the children that preceded; and now, even though she has sons from a Yisrael and from a Levi, since she is married to a kohen she eats Terumah.
"Mes v'lah heimenu ben - tochal biTerumah" - the kohen died and she is left with a son from him: even though she has sons from the others, since her most recent son is from a kohen, she eats Terumah.
The order of descent - as the sons die:
"Mes b'nah mikohen - lo sochal biTerumah" - once the son from the kohen dies, she no longer has a son who entitles her to Terumah, and she is left with sons from men who are not kohanim, from a Yisrael and from a Levi, and therefore she does not eat Terumah.
"Mes b'nah miLevi - lo sochal b'ma'aser" - once the son from the Levi dies as well, she no longer eats ma'aser.
"Mes b'nah miYisrael - chozeres l'veis aviha" - once all her sons from the outsiders have died, and since she is fundamentally the daughter of a kohen, she returns to eating Terumah in her father's house.
About this situation - that her husband died and she has no offspring from the outsider - the mishnah says: "Al zu ne'emar: 'V'shavah el beis aviha kin'ureha, milechem aviha tochel'". "V'shavah el beis aviha" - she returns to her father's house; "kin'ureha" - just as she was in the days of her youth; "milechem aviha tochel" - the bread here refers to her father's Terumah, which she goes back to eating as she did at first.
In summary: in this mishnah we followed the progression of the status of a kohen's daughter: her marriage to a Yisrael forbids Terumah to her, and even his death does not restore it as long as she has a son from him; her marriage to a Levi entitles her to ma'aser, even after his death by virtue of her son; her marriage to a kohen restores her to Terumah, even after his death by virtue of her son from him. And in the reverse order, as the sons die one after another, she falls from Terumah, then from ma'aser, and finally, when she no longer has offspring from the outsiders, she returns to her father's house and to his Terumah - and about this it is said, "V'shavah el beis aviha kin'ureha, milechem aviha tochel".