1)

(a)We can infer from the Mishnah in ha'Choletz 'Yevimto she'Mesah Mutar ba'Achosah' - that 'ba'Achosah In, b'Imah, Lo'!

(b)There is no proof from there for Rav Yehudah however, who says 'Shomeres Yavam she'Mesah, Asur b'Imah' - because, in reality, he is permitted to marry her mother, too, and the reason that the Tana writes ba'Achosah, is because of the Reisha ('Ishto she'Mesah, Mutar ba'Achosah'), which specifically says 'ba'Achosah', as we just explained.

(c)According to Rav Yehudah, we cannot infer from the continuation of the Mishnah 'Asah Bah Ma'amar u'Mes, Sheniyah Choletzes v'Lo Misyabemes' that, if not for the Ma'amar, the Yavam would even be permitted to perform Yibum with the Tzarah - because in his opinion, the Tana writes Ma'amar, not to imply something else, but in its own right, to preclude the opinion of Beis Shamai, who holds that Ma'amar is Koneh completely (in which case the Tzarah will not require Chalitzah either).

2)

(a)The Beraisa rules that if the second brother died before he managed to make Ma'amar with his Yevamah, then the third brother who was born before his death, may perform either Yibum or Chalitzah with his wife. Abaye asks that if, as Rav Yehudah maintains, we hold 'Yesh Zikah', then the second brother's wife ought to be a Tzaras Ervah through the Zikah, and she ought to be permitted l'Shuk because of Tzaras Eishes Achiv she'Lo Hayah b'Olamo'!?

(b)We answer that, according to Rav Yehudah, the author of this Beraisa is Rebbi Meir - who holds 'Ein Zikah' (whereas he follows the opinion of the Rabanan, who hold 'Yesh Zikah').

(c)The problem with saying that Rebbi Meir holds 'Ein Zikah' is that in the Mishnah later, he himself says that if two out of four brothers who married sisters died - the remaining brothers must perform Chalitzah and not Yibum (ostensibly because each one is Achos Zekukaso, from which it appears that he holds 'Yesh Zikah').

(d)In fact, he forbids them to perform Yibum, in spite of the fact that he holds 'Ein Zikah' - because he holds 'Asur l'Vatel Mitzvas Yabmin', meaning that should one of the brothers perform Yibum and his brother dies (before he has managed to perform Yibum with the sister), he will then be unable to perform the Mitzvah of Yibum with her, since she is Achos Ishto.

(e)And we do not permit the second brother to perform Yibum with the second sister, even if his brother performed Chalitzah with the first one - because they decreed there on account of there where the brother performed Yibum first.

3)

(a)The Tana Kama of a Mishnah later rules that if two brothers married two sisters, one a Gedolah and one a Ketanah, and the husband of the Gedolah died, we ask the Ketanah to make Mi'un, because of the Zikah of the Gedolah. Raban Gamliel, says - that if she makes Mi'un, well and good (the Yavam will be able to perform Yibum); and if not, then the Yevamah will have to wait until the Ketanah grows up (and the Kidushin becomes fully effective), when she will be able to marry l'Shuk.

(b)So we see that, although Raban Gamliel holds 'Ein Zikah', he is nevertheless not concerned about 'Bitul Mitzvas Yavmin' - clashing with what we just learned in Rebbi Meir (that 'Ein Zikah', but Asur l'Vatel Mitzvas Yavmin').

(c)We answer that Rebbi Meir is entitled to disagree with Raban Gamliel, and what the questioner really means to ask is - how can it be that Rebbi Meir is concerned even about Safek Bitul Mitzvas Yavmin (that the brother might die without performing Yibum), when Raban Gamliel is not even concerned about Vaday (that the Gedolah will definitely not be able to perform Yibum when the Ketanah grows up)?!

(d)We answer that - it is indeed the case: Rebbi Meir is concerned even about Safek Bitul Mitzvas Yavmin, whereas Raban Gamliel is not even concerned about Vaday.

4)

(a)Rebbi Yehudah ben Beseirah (in a Mishnah in ha'Choletz) rules that if a Yevamah has two Yevamin, one of whom betrothed her sister - we ask the Mekadesh to wait until his brother has performed Yibum before marrying his betrothed ...

(b)... because he holds 'Yesh Zikah'.

(c)Although the Chachamim disagree, Shmuel rules - like Rebbi Yehudah ben Beseirah.

5)

(a)Abaye says that in fact, Rav Yehudah in our Sugya, who holds 'Yesh Zikah' - received this ruling from his Rebbe, Shmuel.

(b)Rav Yosef asked Abaye how he knew that Rav Yehudah did not learn it from Rav (his previous Rebbe). But how can that be, we ask, when we learned above that Rav holds 'Ein Zikah'?!

(c)Rav Yosef answers this by suggesting that Rav's opinion is subject to a Machlokes Amora'im.

(d)Abaye replied - that since we know that Rav Yehudah's opinion conforms with that of Shmuel, it is preferable to establish it like Shmuel, rather than like Rav, which entails creating a new Machlokes Amora'im unnecessarily.

6)

(a)Rav Kahana agrees fully with Abaye. He quotes the statement of Rav Yehudah - explicitly in the name of Shmuel.

(b)Despite the fact that Shmuel has ruled ...

1. ... 'Yesh Zikah', he nevertheless needs to rule 'Halachah k'Rebbi Yehudah ben Beseirah' - to teach us that 'Yesh Zikah;' applies even when there are two Yevamin.

2. ... 'Halachah k'Rebbi Yehudah ben Beseirah', he nevertheless needs to rule 'Yesh Zikah' - to teach us that the Zikah remains even after the death of the Yevamah (because the Zikah does not dissipate automatically (only with the Yibum or the Chalitzah of the Yavam).

7)

(a)Our Mishnah rules that if one of two brothers dies and a third brother is born after the second has already performed Yibum - then, when the latter dies, both of his wives are Patur from Yibum and Chalitzah, because of Eishes Achiv she'Lo Hayah ba'Olamo and her Tzarah.

(b)If the second brother made Ma'amar with the wife of the first before he died - the third brother is obligated to perform Chalitzah with the Tzarah.

(c)When Rebbi Shimon says 'Meyabem l'Eizeh Meihen she'Yirtzeh, O Choletz l'Eizeh Meihen she'Yirtzeh' - he comes to argue with the former case (where the second brother did not perform Ma'amar first).

(d)And his reason is - because since he was born after the second brother performed Yibum, he was not subject to the Zikah that emanated from the first marriage.

8)

(a)From the fact that the Tana finds it necessary to cite the Reisha (the case of 'Nolad v'Achar-Kach Yibem' in the previous Mishnah) - Rav Oshaya extrapolates that Rebbi Shimon must argue even in that case (when the third son was born before the second brother performed Yibum.

(b)According to the Rabanan - it would not be necessary to mention it - because if the third brother is forbidden when he is born after the second brother performed Yibum, then how much more so when he is born before!

(c)Rebbi Shimon does not state his case immediately in the Reisha - because he preferred to wait until the Rabanan had finished speaking before doing so.

(d)The two possible cases of 'Eishes Achiv she'Lo Hayah b'Olamo' which the Torah forbids - are either when there is only one Yavam, or when there are two, but during the lifetime of the second Yavam, as long as he has not yet performed Yibum.

9)

(a)We initially explain Rebbi Shimon's opinion in the Reisha inasmuch as in spite of the fact that the wife of the first brother was still a Shomeres Yavam when the third brother was born, she nevertheless becomes permitted after the death of the second brother - because 'Yesh Zikah, v'Zikah ki'Chenusah Damya' which in effect means that, although the second brother had not yet performed Yibum, it is as if he had.

(b)The Mishnah in Arba'ah Achin discusses the case of three brothers who marry three non-related women. One of the brothers dies and one makes Ma'amar with her before dying too, leaving the two women to the remaining brother. Based on the Pasuk "u'Mes Achad Meihen" - the Tana Kama forbids the Yavam to perform Yibum with a woman who has two Zikos from two husbands. Consequently, he rules 'Choltzos v'Lo Meyavmos'.

(c)Rebbi Shimon (who does not hold of the previous Derashah) says that he may even perform Yibum, but only with one of them; the second one requires Chalitzah. He is ...

1. ... not permitted to perform Yibum with the second one - in case we hold 'Yesh Zikah', in which case they will be two Yevamos falling from the same house (and the second one is forbidden).

2. ... obligated to perform Chalitzah - in case the Halachah is 'Ein Zikah', in which case they are two Yevamos falling from two houses, and both need to be released before they are permitted to marry l'Shuk.

(d)We can extrapolate from this - that Rebbi Shimon is uncertain whether 'Yesh Zikah' or 'Ein Zikah' (or at least 'Ein Zikah ki'Chenusah'), and not like we initially understood (that he holds 'Yesh Zikah' and 'Zikah ki'Chenusah').