496 



Annals of the South African Museum. 



FIG. 5.- V . africanus. Inversion of the embryo (diagrammatic). 



A, B, Preparatory stages, showing denting and incurving of lip of phialopore, and 

 position of gonidia before inversion ; C, early stage of inversion, infolded lip 

 curving back ; D, side view of the same colony, slightly tilted, on a smaller 

 scale ; E, a later stage, the infolded portion opening out ; F, G, inversion 

 nearly complete, but phialopore not yet closed ; F, as seen from the side, G 

 from above ; three pairs of gonidia of different sizes can be seen projecting 

 from the surface of the inverted embryo ; H, detail of relation of gonidium 

 to the somatic cells (1) directly after inversion, (2) later when in-sinking of 

 the gonidium has begun, and (3) in final position. 



D x 150 ; others x 260, approximately. 



