430 Annals of the South African Museum. 



(Eliazer Pan). In July 1930 one of us and Miss Stephens collected 

 Volvox from a large vlei at Old N'gamo, from pools at N'gamo, from 

 quiet backwaters of the Linyanti (Chobe) River, and from pans and 

 vleis left on the south side of this river from the previous wet season. 



All these localities, with the exception of the Linyanti backwaters, 

 are temporary pools * (usually known locally as vleis), the majority 

 of them grass-bottomed, i.e. forming grassy meadowland when they 

 dry up in summer. They occur on soil which is more or less alluvial 

 in character, consisting usually of a mixture of sand and alluvium. 



The paper that follows deals with the results of an investigation of 

 the foregoing samples, together with one from Egypt collected by 

 Mr. Douglas Simpson in 1924. It is apparent that Volvox flourishes 

 abundantly in Africa, and its absence from earlier collections is a little 

 difficult to understand. 



We, like many of our predecessors, realise that considerable varia- 

 tions may occur in one and the same species, not only in the number 

 of constituent cells, in the nature of these cells, in the number of 

 daughter colonies, and in sexuality, but also in the structure of the 

 oospore. There is some doubt as to what should be considered 

 diagnostic features, and there is also some uncertainty as to the 

 number of species of Volvox. The structure of the coenobium has 

 been fully described only in the three European species F. aureus 

 Ehrenberg, F. globator (Linne) Ehrenberg, and F. tertius A. Meyer. 

 The two former are the commonest and best known, and differ from 

 one another as follows : 



1. The coenobia of F. aureus are usually smaller than those of 

 F. globator (the latter measure generally 600 to 800 fi). 



2. In F. aureus the number of constituent cells is from 200 to 4400 ; 

 in F. globator from 1000 to 15,000. 



3. The number of daughter colonies in the asexual coenobia varies 

 from 4 to 14 in F. aureus ; in F. globator the number is usually 8 

 (though it may be more or less). 



4. The protoplasts of the cells of the daughter colonies are separated 



* This is contrary to the experience of Professor lyengar of Madras, who says 

 that in Southern India Volvox has never been collected from temporary rain-water 

 pools (he adds that the trampling of animals tends to make the water of 

 these pools very muddy), but it agrees with the description given by J. H. Powers 

 (" Further Studies in Volvox," Trans. Amer. Micr. Soc., vol. xxviii, 1908, p. 141) of 

 the occurrence of Volvox in parts of America (particularly Nebraska), where Volvox 

 was collected mostly from small rain-pools of scarcely a fortnight's duration, 

 while ponds 1 to 2 ft. deep yielded no Volvox. The forms of Volvox collected in 

 Nebraska are very like the South African representatives. 



