470 Annals of the South African Museum. 



PLATE XVII. 



F. capensis f. rhodesiensis. A and B from N'gamo ; C and D from a pool 



near the wagon road from Kazungula to Kasani, on the Linyanti River. 

 PIG. 



A. Young sexual colony with sperm globoids and oospheres. x 83. 



B. Cell detail from the same colony. x 1000. 



C. Young asexual colony with 19 daughters in early stages of cell division. x 52. 



D. Colony with nearly ripe oospores ; about ten rounded gaps in the cell network 



indicate the positions of escaped sperm globoids. x 63. 



PLATE XVIII. 

 V. Rousseletii (Mr. Steer's Rietfontein culture). 



A-D. Successive phases showing varying proportions of asexual to sexual col oaies 

 and varying numbers of daughter colonies. Description in text. 



E. Mature daughter in situ showing gonidia (under cover slip). 



A and D x 15. B x 12. C x 25. Ex 150. 



PLATE XIX. 

 F. Rousseletii (Mr. Steer's Rietfontein culture), cell detail. 



A. Living cells from the anterior pole of a mature colony, showing shape and 



position of eyespots, and insertion of cilia. x 1000. 



B. Cells from the anterior pole, and C, from the posterior pole, of a middle-aged 



colony killed with iodine. x 800. 

 D, E. Similar cells (living) from an older colony. x 900. 



PLATE XX. 

 F. Rousseletii, from Rietfontein. 



A. Asexual colony showing arrangement of daughter colonies (8th gonidium, 



abortive, on the right). 



B. Mature male colony ; C, mixed colony with 3 daughters and numerous sperm 



globoids. 



D-F. Female colonies : D, still young, some oospheres not yet fertilised ; E, F, 

 nearly mature. 



A and F x 60. B and D x 65. C x 50. E x 70. 



PLATE XXI. 

 V. Rousseletii (Mr. Steer's Rietfontein culture). 



A. Free sperm globoid (killed with csmic acid) in surface view. x 750. 



B. Young globoid soon after inversion, in side view. The line of demarcation 



between green base and colourless anterior portion shows clearly. x 1000. 



C. E. Nearly mature oospores in situ. x 800 and x 325 respectively. 



D. Mature oosphere in side view. x 800. 



