VOLVOX GLOBATOR 



263 



ovy 



H 



FIG. 65. Volvox globator. 



A, the entire colony, surface view, showing the biflagellate zooids, and 

 several daughter-colonies swimming freely in the interior : the latter are 

 produced by the repeated fission of non-flagellate reproductive zooids 

 (a). 



B, the same during sexual maturity, showing spermaries from the 

 surface (spy], in profile (spy'} and after complete formation of sperms 

 (spy"} : and ovaries from the surface (ovy, ovy", ovy'"} and in profile 

 (ovy'}. 



C, four zooids in optical section, showing cell-wall, nucleus, contractile 

 vacuole, with adjacent pigment-spot, and flagella. 



D^D 5 , stages in the formation of a colony by the repeated binary 

 fission of a sexual reproductive zooid. 



E, a ripe spermary. 



F, a single sperm, showing pigment-spot (pg) and flagella (ft). 



G, an ovary containing a single ovum surrounded by several sperms 

 H, oosperm enclosed in its spinose cell-wall. 



(A from Geddes and Thomson, after Kirchner ; B-H after Cohn.) 



