156 Dr. C. A. Kofoid on Pleodorina illinoiselisis. 



Migula, W. (1830.) — " Beitrage zur Kenntniss des Gonium pec* 



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



Taf. ii. 

 Mother, D. M. (1891.) — " Pleodorina in Indiana," Botan. Gazette, 



vol. xix. p. 383. 

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



Botan. Centralbl. Bd. xxxix. pp. 65-72, ] 13-118, 145-150, 177- 



182, 209-214, 241-246, 273-279, Taf. i.-iii. 

 Pfeffer, W. (1884.) — " Locomotorische Richtungsbewegungen 



durch chemische Reize." Untersucli. a. d. botan. Inst, zu Tubingen, 



Bd. i. pp. 363-482. 

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



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

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



Volvox globator? Midland Naturalist, vol. iii. pp. 209-214, 233- 



237, pis. vii., viii. 



EXPLANATION OF THE PLATES *. 



Abbreviations. 



A. Anterior pole. ncl. Nucleolus. 



chr. Chromatophore. o.l. Outer layer of sbeatb. 

 cm. Cell-membrane. P. Posterior pole. 



/. Flagellum. p.c. Protoplasmic column. 



fn. Furrow. pr. Pyrenoid. 

 g.c. Gonidial cell. r. Reticulum. 



i.l. Inner layer of sheath. s. Stigma. 



m. Matrix. sh. Sheath. 



nun. Matrix membrane. v.c. Vegetative cell. 

 n. Nucleus. I, II, III. Cleavage planes. 



Plate V. 



Fhj. 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. f 



Fig. 7. Pleodorina ffli?ioisensis, 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 16-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. 



