Sellaphora auldreekie: mature gametangia immediately before plasmogamy. A small copulation aperture has been formed between the gametangia and the gametes push out into this and touch. The  nucleus of each gamete (e.g. arrow) lies Immediately beneath the copulation aperture; it contains a small nucleolus. At this stage, the chloroplasts still lie on opposite sides of the mating pair, as during meiotic prophase.