Volvox and Associated Algae from Kimberley. 513 



SUMMARY. 



1. Volvox has been found in three temporary rain-water pools in 

 quarries near Kimberley ; these pools may fill and dry up several 

 times during a single season, Volvox disappearing before the pool is 

 dry and reappearing soon after it refills. 



2. Of these three pools the first one found Pool I was visited 

 repeatedly from November 1931 to the beginning of April 1932, 

 during which time it came into existence on three separate occasions, 

 the duration of the pool varying from three to five weeks, alternating 

 with periods of dryness varying from a few days to several weeks. 

 On each visit collections were made and preserved in formalin or 

 iodine. The other two pools were not discovered until late in the 

 season, after the last heavy rain, and the collections from these are 

 consequently few and scanty. 



3. Three species of Volvox were found : one, a local variant of the 

 widespread V. Rousseletii, was common to all three pools ; the second, 

 a startlingly large one, sometimes as much as 3 mm. in diameter, is 

 diagnosed as a new species to which the name Volvox gigas is given. 

 It was found in Pool I only. The third is a very large form of Volvox 

 africanus G. S. West, usually containing four pairs of embryos ; it 

 occurred in small quantities, entirely asexual, in Pool II only. 



4. In Pool I three other algae are associated with the two species 

 of Volvox, namely: 



(a) Eudorina elegans, mainly large colonies, occurring in small 



quantities in the tubes, probably very much more numerous 

 in reality ; 



(b) An interesting, very polymorphic gelatinous non-motile alga, 



described as a new species, Sphaerocystis Poweri, one form of 

 which eventually becomes the dominant alga in the pool ; 

 and 



(c) A large, very many celled species of Kirchneriella, described as 



K. africana sp. nov. 



5. The phytoplankton of Pool I shows an interesting succession, 

 of which the following are the main phases : 



(a) Volvox Rousseletii dominant, Sphaerocystis present in small 



quantities, and, towards the end, young colonies of V. gigas. 



(b) Volvox Rousseletii becoming less numerous, V. gigas increasing, 



sometimes becoming dominant, Sphaerocystis and Kirch- 

 neriella increasing ; 



