64 



MEMOIRS OP THE UNIVERSITY OF CALIFORNIA 



mainly and forming a loose network over the entire cell, the branches anasto- 

 mosing at various points. The interior of the cell is sometimes filled with a 

 single large vacuole, sometunes by several, ^^ith strands of protoplasm extending 

 through it from the main portion around the nucleus. 



Fig. I 



Fig. I. Life cycle of Gymnodinium lunula Schiitt. After Dogiel (1906, pi. 1) with some modifications. 

 Pyrocystis stage, 1-7. Gymtiodinium stage, 8-11. 1. Large globular form. Besting spore? 2. Formation of 

 first cleavage nuclei. Protoplasmic body shrinking away from cyst waU. Primary cyst stage. 3. Second 

 cleavage with fourth division of nuclei completed. 4. Formation of crescent-shaped spores. Secondary cysts. 

 5. Single spore released from the cyst. 6. Beginning of division of the spore. 7. Completion of spore divisions 

 with the formation of eight Gymnodinium individuals. S. G. lunula escaped from cyst. 9. Formation of ter- 

 tiary cyst. 10. Division of encysted individual. 11. Individual escaped from cyst. Encystment may take 

 place, repeating 9-11 many times before the next stage is begun. The change from 11 to 1 is unknown. X 330. 



