On Pleodorina illinoisensis. 



293 



EXPLANATION OF PLATES.* 



ABBREVIATIONS. 



A., anterior pole. 

 chr., chromatophore. 

 c. m., cell membrane. 

 /., rlagellum. 

 /it., furrow. 

 g. c, gonidial cell. 

 i. I , inner layer of sheath. 

 hi., matrix. 

 »n. m., matrix membrane, 

 n., nucleus. 



wcZ., nucleolus. 



0. £., outer layer of sheath. 

 P.. posterior pole. 



p. c, protoplasmic column, 

 pr., pyreuoid. 

 /•.. reticulum. 

 s., stigma. 

 s/(„ sheath. 

 v. c, vegetative cell. 



1. II, 111, cleavage planes. 



Plate XXXVI. 



Pleodorina illinoisensis, lateral view of colony. X 500. 



Lateral view of vegetative cell. X 1500. 



Lateral view of gonidial cell. X 1500. 



Lateral view of matured colon}', showing posterior lobes. 



X 185. 

 Diseased cell, early stage. X 1250. 

 Diseased cell, later stage. X 1250. 



Plate XXXVII. ' 



FlG. 7. Pleodorina illinoisensis, top view of 2-cell stage. 



Fig. S. Top view of 4-cell stage. 



Fig. 9. Lateral view of 4-cell stage. 



Fig. 10. Top view of 8-cell stage. 



Fig. 11. Lateral view of 8-cell stage. 



Fig. 12. Top view of 16-cell stage. 



Fig. 13. Lateral view of 16-cell stage. 



Fig. 14. Top view of 32-cell stage. 



* Figures drawn by C. A. Kofoid and inked by Miss 1.. M. Halt. 

 1 Figs. 7-11 magnified loon diameters. 



