42G 



G. S. WEST ON 



Afiican material, althougli from a previous observation on material 

 from Ugcinda it seems probable that the male colony is similar 

 to that of F. aureus * On the other hand, both male and female 

 colonies of F. Rousseletii were abundant. The outstanding feature 

 in both species is the relatively large number of ripe oospores in 

 the female colonies. In F. Rousseletii not only were there purely 

 male colonies (figs. 1 and 7), but also male colonies which, in addi- 

 tion to numerous antheridia, possessed daughter-colonies which 

 had arisen from parthenogonidia (fig. 2). 



There is a marked polarity in all the sexual colonies. The 

 vegetative colonies of F. Rousseletii are approximately spherical, 

 but both male and female colonies are egg-shaped with a general 

 concentration of the sexual elements towards the narrower pole 

 (consult all the figures of colonies). 



The following tabulated statements indicate the difi'erences 

 between the two African species : 



Volvox Rousseletii. 



G. S. West. 



Vegetative colonies subglobose ; 

 diameter, 1,125-1,240 ^t. 



Number of cells, 25,000-50,000. 



Cells small, very densely aggre- 

 gated, 4-6'5 /Lt in diameter, some- 

 what angular with relatively broad 

 connecting strands of protoplasm. 



Daughter-colonies, regularly 8. 



Oospores, 120- 150 (average 12 8), 



densely clothed with strong conical 



spines ; average diameter without 



spines, 44 /i ; length of spines, 



11-12 ft. 



Androgonidia (and subsequently 

 antheridia) very numerous in each 

 male colony (usually several 

 hundred). 



Antherozoids and oospheres 

 produced in different colonies. 



Volvox africanas. 

 G. S. West. 



Vegetative colonies ovoid- 

 ellipsoid ; length, 345-610 fi; 

 breadth, 295-480 /x. 



Number of cells, 3,000-8,000. 



Cells less densely aggregated, 

 8-9"5 fi in diameter, almost glo- 

 bose with long delicate connecting 

 strands of protoplasm. 



Daughter-colonies, 1-4. 



Oospores, 70-80 (average 74), 

 with a thick smooth wall ; aver- 

 age diameter, 45 /u. 



Androgonidia not yet observed 

 with certainty (but probably very 

 numerous). 



Antherozoids and oospheres 

 produced in different colonies ? 



[This is probable, since only 

 female colonies have so far been 

 definitely observed.] 



* G. S. West, I.e. p. 103. 



