1. The opening through which the swarm spore escapes is made by some chemical change, probably enzymatic, which is initiated and controlled by the chloroplast. 2. Zoospores escape by an amoeboid movement through a pore. 3. There is a period of quiescence after the escape of the spore, at the end of which the cilia appear. 4. The second wall in the sporeling of C. scutata is almost invariably a double curved line whose openings are turned in opposite directions. This wall passes through the long diameter of the cell. 5. The first two cells of the sporeling of C. orbicularis and C. soluta divide to form four or six cells. By division of these the thallus is formed. 6. C. soluta is developed into a thallus, with no indication of the filamentous character except the small space between the outer cells of the mature thallus. 7. Hair formation is initiated by a stream of cytoplasm issuing from one or two granules, found either in the lower part of the pore or in the outer open end of the cylindrical chloroplast...