| Abstract: | Reproductive stages of a Helicodictyon planctonicum strain from Pennsylvania were observed in cultures. The adult colonial form is enclosed within a mucilaginous matrix and contains a gas bubble. In older cultures some colonies lose their gas bubbles and sink to the bottom of the culture solution. When these colonies from the bottom of old cultures are transferred to fresh medium, their cells become transformed into biflagellate motile cells. Motile cells fuse in pairs to form zygotes. Some motile cells lose motility and develop directly into adult colonies without prior fusion. |
