1. The current figures and descriptions of the chromatophore of Closterium derived from Nageli are fundamentally incorrect. The chromatophore is not made up of a series of radiating plates about a slender central core, but is a curved cone-shaped structure with relatively narrow ridges on its surface. 2. The pyrenoids are imbedded in the periphery of this chromatophore in C. Ehrenbergii and exactly at its center in C. moniliferum. 3. Pyrenoid starch and stroma starch both have the same origin, all the starch being formed around pyrenoids. 4. The pyrenoids show considerable internal structure, frequently containing denser and lighter portions, vacuoles, etc., and often are cleft into a mass of disks or segments of varying number and form.