484 



Annals of the South African Museum. 



gonidium is distinguished from the somatic cells by its larger size and 

 more numerous pyrenoids; the apex of the chloroplast is lobed, so 

 that the colourless anterior area appears more or less star-shaped 



FIG. 2. Volvox gigas. 



A, Somatic cell from anterior pole ; B, young gonidium and two somatic cells ; 

 C-0, development of the embryo ; C, gonidium viewed from above ; D, first 

 division; E, F, four-celled stage seen from above and in side view; G, eight- 

 celled stage ; H-O, inversion of fully formed embryo ; H and J, preparatory 

 stages in optical section ; K, general view ; L-N, actual inversion in process ; 

 O, inversion complete, cilia appearing (L-0 semi-diagrammatic). 



A, B x 500 ca. ; C-F x 250 ca. ; H-O x 350 ca. 



when seen from above (fig. 2, C). The cilia are lost early in the 

 period of enlargement. 



As is the case throughout the group, the first two divisions of the 

 gonidium are longitudinal, in two radial planes at right angles to one 

 another. The separation of the apices of the resultant cells is apparent 

 even in the 2-celled stage (fig. 2, D), while the hollowing to form a 



