Continuing from the attempted line up of the positions of Beit Hillel and Beit Shammai by R. Yochanan, including his willingness to reverse their positions (the Gemara pushes back). Plus, a new mishnah! With a new machloket between Beit Shammai and Beit Hillel, which may revolve around the questions of bereira, again (retroactive designation). And another mishnah too: you go to choose birds from the dovecote that you have already designated, and they are apparently not there... Now what? The birds need to be the ones that were designated if they are to be used in sacrifice. Plus other examples of designation vs. that which is not designated, where they get mixed and the mixture is not discernible.