Prochloron

Three species:

Prochloron - a unicellular marine organism symbiotic on sea squirts. Discovered 1976. Chlorophlylls a and b; carotenoids
An electron photomicrograph of a cell of
Prochloron. Concentric layers of membranes perform
organelle functions.

Prochlorothrix - free living capable of growing in culture. Discovered in Holland.
Unnammed organism - discovered in late '80's. Appears to be one of the two most numerous bacteria living in ocean waters.
The discovery of these organisms adds weight to the theory that chloroplasts may have originated from cells liviing within cells.