Volvox and Associated Algae from Kimberley. 505 



spherical phase, but smaller, usually show no grouping, but some- 

 times grouping in fours or even eights is very marked. This 

 probably depends on the rate at which division is proceeding unless 

 the rate is high the daughter cells separate before the next division 

 takes place, and all trace of grouping is lost. In some colonies the 

 number of zoospores among the round cells is very great. 



The four stages are so very distinctive that were it not for the 

 intermediate stages which occur they might easily be taken as 

 belonging to different genera. 



The entire absence from all stages except that of the motile zoo- 

 spores of any trace of cilia or pseudocilia distinguishes this genus 

 not only from the Tetrasporaceae, but also from Gloeococcus, as denned 

 by Braun. It is difficult to understand the view taken by Wille 

 (1903) and Lemmermann (1915, p. 31) in regarding Sphaerocystis 

 Chodat as identical with Braun's genus, since Braun in his definition 

 of the genus (as quoted by Eabenhorst, 1868, iii, p. 36) explicitly 

 describes the presence of cilia : " Cellulae ovales, virides, in parte 

 antica ciliis vibratoriis binis . . . instruct ae " (cf. also Chodat, 1904, 

 p. 233), and in the following description amplifies this, stating that : 



The cells in all the succeeding generations which take place during 

 the formation of these families except the transitory generations (in 

 the case of repeated division) are provided with two very long per- 

 sistent moving cilia which only disappear at the beginning of division " 

 (Braun, 1851, quoted by Chodat), whereas in Sphaerocystis cilia are 

 present only in the zoospores. 



In the Kimberley material the palmelloid colonies may reach a 

 fair size, up to 3 or 4 mm. in length, but this is a very different matter 

 from families the size of an apple or a hazel-nut which characterise 

 the two species of Gloeococcus on which Braun founded his genus. 



W. and G. S. West (1912, p. 413) found that Sphaerocystis Schroeteri 

 formed a large part of the phytoplankton of Loch Lomond during the 

 warmer months only (July to October), and was not seen during 

 the colder periods of the year. Although even then the temperature 

 of the water (59 F. or 15 C.) was very much lower than that of the 

 Kimberley pool (25 to 30 C.), yet the observation is suggestive. No 

 doubt, at least, a part of the associated palmelloid material which 

 these workers diagnosed as Tetraspora lacustris was actually the 

 corresponding form of Sphaerocystis, since it is evident that pseudo- 

 cilia were not seen in this material (West, 1916, p. 186). 



The spherical form of Sphaerocystis Poweri differs from Sphaerocystis 

 Schroeteri Chod. (1897a, p. 119, and 18976, p. 292), in the very great 



VOL. XVI, PART 3. 33 



