The article presents a brief review of the latest experimental data on sexual reproduction in the colonial volvocine algae, which represent a promising model for research on developmental biology. The main focus is on the MID gene, which determines sex and controls the “minus”/male differentiation in iso-gamous, anisogamous, and oogamous volvocine species. The experiments on sex transformation in a model species Volvox carteri f. nagariensis are critically analyzed. Studies of the gene FUS1, which controls gamete recognition and fertilization in the isogamous and anisogamous volvocine algae, are also considered.