Observations on the Genus Volvox in Africa. 447 



The colour of the protoplast changes from green to orange-red, and the 

 oospore is ready for liberation, which is brought about by the disinte- 

 gration of the parent. This takes place very soon after the change in 

 colour, so that on the Cape Flats colonies containing ripe oospores are 

 remarkably rare (Plate XIII, fig. E, and Plate XV, fig. E). 



Oospores in various stages of development are shown in text-fig. 4, 

 C, 1-3. 



Dimensions, etc., of V. capensis from the Cape Flats. 



Mature asexual colony, 667 x 754 /z to 1250 x 1292 ^ ; average about 



800 x 850 /z. 

 Mature sexual colony, 495 x 560 ^ to 928 x 1034 /z ; average about 



625x660^. 

 Mature daughter colony, 129 x 139 ^u, to 431 x 495 /z ; average about 



200 x 230 fj,. 



Somatic cell : anterior pole 12 to 18 /z ; posterior pole 11 to 13 p. 

 Somatic protoplast : anterior pole 6 to 11 JJL ; posterior pole 5 to 9 /x ; 



average 5 to 7 /z. 



Somatic protoplast in daughter colony before birth, 4 to 5 /z. 

 Gonidium protoplast in daughter colony before birth, 11 to 13 fj,. 

 Sexual cell protoplast in daughter colony before birth, 6 to 7 /x. 

 Number of somatic cells, 9000 to 23,000, most often 18,000 to 20,000. 

 Number of daughter colonies, 4 to 12 ; in very warm weather up to 20. 

 Number of sperm globoids, 5 to 13 ; in very warm weather up to 19. 

 Number of oospores, 60 to 160 ; average 120. 

 Size of sperm globoid, 33 to 44 p.. 

 Size of oospore with spines, 49 to 62 /z ; without spines, 37 to 49 p. ; 



spines, 5 to 8 JJL. 



2. V. capensis forma rhodesiensis f. nov. 



Forma magna, antheridiis numerosioribus, usque ad 35, oosporis 

 majoribus quam in forma typica. 



From N'gamo and Old N'gamo in Rhodesia, and from vleis and 

 backwaters of the Linyanti, Bechuanaland Protectorate.* 



(a) From N'gamo and Old N'gamo (Southern Rhodesia). 



Near N'gamo station there are several small vleis from which Volvox 

 was collected at the beginning of July 1930. The following day the 

 vlei at Old N'gamo, 5 miles north, was visited ; Volvox was collected 



* Geographically parts of both Northern and Southern Rhodesia and the 

 Bechuanaland Protectorate are one region. Their boundaries meet on the Linyanti 

 near Kazungula, hence the regional name may appropriately be used for the form. 

 The word X'gamo is probably of Bushman origin, meaning water. 



