Observations on the Genus Volvox in Africa. 437 



Old N'gamo (and also at N'gamo) possesses asexual colonies like those 

 described by West for Rhodesia, the sexual colonies associated with 

 them are not of the type described from Ussangu and presumed by 

 him to belong to the same species. 



In any case, the existence of two distinct types has been established, 

 and we have been fortunate enough to obtain from Rhodesia and other 

 localities sexual and associated asexual colonies of both types the 

 Ussangu type from Egypt, Rietfontein (Transvaal), and Sedudu (N. 

 Bechuanaland Protectorate), and the Old N'gamo type from the 

 Cape Flats as well as from other parts of Rhodesia and the Bechuana- 

 land Protectorate. 



The main point of difference between these two types is that in one 

 the sexual colonies are dioecious, in the other they are monoecious. 

 Now, whereas in V. globator the sexual colonies are consistently 

 monoecious, it is well known that in V. aureus monoecious as well as 

 the more usual dioecious colonies may occur, and we should hesitate 

 to make this a character of diagnostic importance were it not for 

 (a) its constancy in a particular type, and (b) its association with other 

 slight but well-defined differences. 



With regard to (a), cultures of the Rietfontein Volvox have been 

 watched constantly for a period of over eighteen months, and the 

 colonies have been found to remain dioecious, with very rare excep- 

 tions in which a few antheridia developed in otherwise preponderat- 

 ingly female coenobia (the reverse oospores in a male coenobium 

 was never once seen), while the Cape Flats Volvox during some years 

 of observation (which was particularly close and detailed in. 1930 and 

 1931) has been found to be consistently monoecious.* These two 

 examples, from Rietfontein and from the Cape Flats, are cited in 

 particular, since they are the two whose life-history has been methodi- 

 cally observed, but collections of Volvox from elsewhere appear to 

 confirm these observations. 



In view of the existence of these two types we propose to create a 

 new species to include the type found at Old N'gamo and on the Cape 

 Flats, and, since it has been fully known longer from the latter locality, 

 to name it V. capensis. It will be seen that this species shows several 



particularly wet rainy season, and it seems probable that Volvox does not develop 

 in that region until later in the season when the water has grown shallower. It is 

 obviously widespread in Rhodesia. 



* Ths results of these observations are embodied in a paper by M. A. Pocock 

 forming the thiid of the series on Volvox in Africa, and appearing in Part 4 

 of this volume. 



