Volvox and Associated Algae from Kimberley. 479 



impossible for Volvox. Eventually, as the water dried they formed 

 a compact gelatinous mass at one end of the pool. Further, if the 

 pool refilled even after a very short period (in one case only three or 

 four days) of dryness, V. Rousseletii developed again with great 

 rapidity (cf. Phase 3), yet if rain refills it towards the end of a phase 

 when the Volvox has already disappeared, but before the pool has 

 quite dried up, this alga does not reappear. This is seen at the end 

 of this same phase, when on 18th March light rain prolonged the life 

 of the pool. Although collections were made for twelve days after 

 that date, in all of which the non-motile algae were most abundant, 

 only occasional colonies of V. gigas were found and no V. Rousseletii. 

 This seems to indicate the need for at least a brief period of dryness 

 to mature the oospores of the latter form of Volvox before they can 

 germinate. 



PART II. DESCRIPTION OF THE SPECIES. 



A. VOLVOCALES. 



I. Genus EUDORINA Ehrenberg. 

 Eudorina elegans Ehrenb. 



Coen 53-215^x62-258^ 



Cell 19^ 



Coen. c. embryon. . 366 x 430 /z. 



Embryon. . . 44 x 53 jit 



Occasional, among Volvox, etc. in Pool I, particularly during the 

 earlier stages. 



Except for its somewhat unusually large size this material seems to 

 conform to typical E. elegans. Mostly large 32-celled colonies, often 

 with daughter colonies fully formed, were seen, small colonies being 

 very rare. In some, all the 32 cells had formed daughter colonies ; 

 in others, several cells had remained undivided. 



It is probable that this species is actually far more abundant than 

 the number of colonies noted would indicate, since the collecting was 

 done mainly for Volvox and not for the finer plankton. 



