[27a - 42 lines; 27b - 34 lines]
1)[line 11]מאמרMA'AMAR YEVAMIM
(a)If a married man dies childless, his widow may not marry whomever she pleases. She first must undergo Yibum (levirate marriage, that is, she must marry her dead husband's brother), as the Torah states in Devarim 25:5-10. The only way to perform Yibum mentioned in the Torah is through marital relations with her. Giving her money (Kidushei Kesef) or a document (Kidushei Shtar) does not achieve marital ties between them as it does with a woman who is not a Yevamah (GEMARA Kidushin 4b). As RASHI writes (Yevamos 52a DH Nasan), it is impossible to effect Kidushin with one's brother's wife because Kidushin do not "take hold" ("Einam Tofsin") on an Ervah (see Insights to Yevamos 20:3).
(b)However, Chazal did enact a process called "Ma'amar" for a Yevamah, in which the Yavam can "effect Kidushin" with his Yevamah in a manner equivalent to Kidushei Kesef or Shtar in normal Kidushin. It is called Ma'amar since it is an institution of the Chachamim ("Ma'amar Chachamim" - HAGAHAH to SHULCHAN ARUCH Even ha'Ezer 170:2). They decreed that a Yavam should make "Kidushei Ma'amar" before he has relations with her for the sake of the Mitzvah of Yibum, for reasons of modesty (Yevamos 52a). Kidushei Ma'amar are like an introduction to the act of Yibum. If the Yavam decides not to go through with the Mitzvah of Yibum, he must give the Yevamah a Get to remove the status of Ma'amar. (The Gemara discusses whether this "Kidushin" is exactly similar to normal Kidushin, and may not be performed against the will of the woman, or if it is slightly similar to the Mitzvah of Yibum, and therefore may be performed against her will - Yevamos 19b.)
(c)Since Ma'amar does not effect a full acquisition of the Yevamah as the wife of the Yavam as does Yibum, the bond of Zikas Yibum between them still exists. Therefore, if the Yavam wishes to divorce the Yevamah after Ma'amar, a Get (bill of divorce) is not enough; he must perform Chalitzah in order to render her free to marry whomever she pleases, besides divorcing her with a Get. Thus, if the Yavam wants to "divorce" the Ba'alas ha'Ma'amar before Yibum, he must both give her a Get and perform Chalitzah.
(d)According to the conclusion of the Gemara (Yevamos 29b, as understood by most of the Rishonim), Beis Shamai disagrees with what has been presented above, and rules that Ma'amar effects a full acquisition of the Yevamah mid'Oraisa, not only mid'Rabanan. According to some Amora'im, Beis Shamai even rules that if the Yavam wants to divorce the Yevamah after Ma'mar, a Get is enough and Chalitzah is not required (ibid.). [However, RASHI (Yevamos 29b DH Hashta) explains that even according to Beis Shamai, Ma'amar is only mid'Rabanan, see Insights ibid.] Other Tana'im are in doubt as to whether Ma'amar effects an marriage to the Yevamah mid'Oraisa or only mid'Rabanan (Rebbi Shimon, Yevamos 18b).
2)[line 21]אלא צרה דלאה תיפטרELA TZARAH D'LE'AH TIPATER?- see Insights
3)[line 26]התחיל באחיות לא יגמור בצרותHISCHIL BA'ACHAYOS, LO YIGMOR B'TZAROS- that is, if the first Chalitzah was performed with one of the sisters (e.g. Le'ah), Chalitzah with one Tzarah (the Tzarah of Rachel) will suffice and the second Tzarah does not need Chalitzah or Yibum.
4)[line 32]תניא כוותיה דרב אשיTANYA KAVASEI D'RAV ASHI- (Although the Beraisa uses the same terminology as Shmuel, the Gemara assumes that it cannot mean what we previously asserted that Shmuel meant. Shmuel might have chosen a slightly ambiguous terminology in order to use a single set of words to describe the Halachah in three different cases (Chalatz la'Achayos, Chalatz l'Ba'alas ha'Get, and Chalatz l'Ba'alas ha'Ma'amar). The Beraisa, however, which discusses only the former of the three, should have chosen a more accurate terminology. -TOSFOS)