A new chapter! With an introduction to the basis of the laws of inheritance. Including the rules of the first-born, and referring to the daughters of Tzlofchad. The first mishnah gives the list of who inherits and bequeaths to each other, who inherits but doesn't bequeath, doesn't inherit, but does bequeath, and neither. The Gemara wants to address the order of these cases -- including the fact that the sages did not want to begin the mishnah with calamity. Plus, cases reminiscent of Yevamot with cases of yibum and inheritance.