Volvox in South Africa. 643 



C-K. F. Rousseletii. Inversion ; living, all x 200. 

 FIG. 



C, 11.10 a.m. Preparation ; colony dented, lip depressed (262). 



D, 11.55 a.m. Denting more extensive, lip rising (263). 



E, 12.5 p.m. Dents disappearing, lip straightening (264). 



F, 12.10 p.m. Dents smoothed out, lip nearly straight (265). 



G, 12.15 p.m. Beginning of inversion proper " Hour-glass " stage, equatorial 



constriction appearing (266). 

 H, 12.17 p.m. Contraction extending over posterior hemisphere, cells sharply 



pointed, pore opening (267). 

 I, 12.24 p.m. Infolding beginning (268). 



J, 12.30 p.m. Half infolded, pore enlarging, connections breaking (269). 

 K, 12.45 p.m. Connections with parent broken, colony turned over showing polar 



view of " Flask " stage with contracting pore (270). 



PLATE XLI. 



Inversion of daughter colony, continued. 

 A. I', capensis. Preparation. 



Lower central daughter from colony above (Plate XL, B) a few minutes later 

 dents have disappeared, lip is still depressed, gonidia visible. Living (548). 

 x300. 



B-I. V. Bousseletii. Inversion. 



B-F. Series showing later stages in inversion. Living. x 200. 



B, 12.20 p.m. Infolding complete (241). 



C, 12.22 p.m. Beginning of " Hat " stage, posterior part (to become anterior pole 



of inverted colony) beginning to emerge through pore (242). 



D, 12.27 p.m. End of " Hat " stage (243). 



E, 12.29 p.m. " Flask " stage (244). 



F, 12.36 p.m. End of " Flask" stage, pore contracting, lip rapidly closing (245). 



G, Another larger colony partly infolded, showing more detail cells in anterior 



part stretched and pulled apart, those in posterior half compressed, sharply 

 pointed, and very dense. Living (254). x 200. (See text-fig. 4, A, B.) 



H. Section through a colony in the same stage, showing "pointing" of posterior 

 cells (513). x300. 



I. Section of " Flask " stage, intermediate between E and F (530). x 300. 



PLATE XLII. 

 V. Bousseletii. Development of male initial cell (living). 



A-E. Period of enlargement : A shows 2 young ciliated male initials in different 

 stages (213). x 1000. B, a very young stage in surface view (250). x 1300. 

 C, cilia lost (195). x 1000. D, surface view showing nucleolus (335). 

 x 1000. E, enlargement complete (336). x 1000. 



F. Rotation of physiological axis nucleolus lies inwards on left. The arrow 

 indicates the position of the axis (186). x 940. 



G-N. Period of cell-division. 



