156 l)r. C. A. Kofoid on Pleodoriiia illinoisensis. 



MiGULA, W. (1890.) — " Beitra<»e zur Kenntniss des Goniuin pec* 



torale," Botan. Centralbl. Bd. xliv. pp. 72-76, 103-107, 143-146, 



Taf. ii. 

 MoTTiKR, D. M. (1894.) — *' IHeodorina ia Indiana,'' Botan. Gazette, 



vol. xix. p. 383. 

 Overton, E. (1889.) — "Beitrag zur Kenntniss der Gattung Vohox" 



Botan. Centralbl. 13d. xxxix. pp. (m-72, 113-118, 145-150, 177- 



182, 209-214, 241-240, 273-2r;>, Taf. i.-iii. 

 Pfkffek, "W. (1884.) — " Locomotovisehe Richtimgsbewe^ungen 



diirch cheniische Keize,*' Untei-such. a. d. botan. Inst, zu Tubingen, 



M. i. pp. 303-482. 

 Shaw, W. R. (1894.) — " Pleodoriiia, a new Genus of the Volvocinege,'' 



Botan. Gazette, vol. xix. pp. 279-283, pi. xxvii. 

 Wills, A. \V. (1880.) — "On the Structure and Life-History of 



J'olvo.v fflobatov,"' Midland Naturalist, vol. iii. pp. 209-214, 233- 



237, pis. vii., viii. 



EXPLANATION OF THE PLATES *. 



A. Anterior pole. 

 chr. Chromatophore. 

 cm. Cell-membrane. 



/. Flagellum. 

 fu. Furrow. 

 g.c. Gonidial cell. 

 i.l. Inner layer of sheath. 

 m. Matrix. 

 m.m. Matrix membrane. 

 II. Nucleus. 



Firj. 1. Pleodorina illinoisensis, lateral view of colony. X 500. 



Fig. 2. Lateral view of vegetative cell. X 1500. 



Fig. 3. Lateral view of gonidial cell. X 1500. 



Fig. 4. Lateral view of matured colony, showing posterior lobes. X 185. 



Fig. 5. Diseased cell, early stage. X 1250. 



Fig. 6. Diseased cell, later stage. X 1250. 



Plate VI. t 



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



Fig. 8. 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 10-cell stage. 



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



* Figures drawn by C. A. Kofoid and inked by Miss L. M. Hart, 

 t Figs. 7-14 magnified 1000 diameters. 



