Volvox and Associated Algae from Kimberley. 517 



DESCRIPTION OF PLATES. 



The number in brackets at the end of each description denotes the reference 

 number of the original negative. 



PLATE XXV. 



Volvox gigas sp. nov. 

 PIG. 



A. Group, four large asexual colonies with young embryos and gonidia, and a 



very young colony ; in the centre an asexual and a mature male colony of 

 F. Rousseletii forma griquaensis (602). 



Dimensions : T'. gigas (1) 2000 /(, (2) 2148 x 2590 /i, (3) 2222 x 2660 //, 

 (4) 2814 x 3111 /<. V. Rousseletii : asexual 1111 //, male 740 x 880 ft.. 



B. Male and female colonies, the latter with large scattered oospheres ; the male 



colony in B2 typically egg-shaped. In both males all the cells in the posterior 

 part of the colony are developing into sperm bundles ; spaces among the 

 cells show where sperm bundles have already escaped (627). 



C. Small mature colony with few-celled embryos, probably males (compare with 



Plate XXVI, E), and a few oospores (694). 



D. Group, showing very young and nearly mature asexual colonies (one with 



between 50 and 60 embryos), mixed colonies with eggs and embryos, and 

 pure male and female colonies ; at the top left-hand corner are two spherical 

 and three or four palmelloid colonies of Sphaerocystis Poweri, while near the 

 bottom right-hand corner is a small spherical colony beginning to show 

 transition to the palmelloid state (639). 



A xl3-5. B x25. C x 38. D x 16. 



PLATE XXVI. 

 Volvox gigas. Stages in development of asexual colonies. 



A. Young colony with undivided gonidia, many still enlarging (634). 



B. Older colony with several embryos inverting (631). 



C. Daughter colonies fully formed but still very small. Colony 2283 x 2498 ft, 



with 64 daughters (629). 



D. Colony with 42 daughters in various stages of enlargement, gonidia distinguish- 



able in the larger (618). 



E. Daughter colonies 28, mature and ready for escape ; gonidia distinct. On the 



right, part of a colony with recently inverted daughters (617). 



F. Inverting embryo in " Hat " stage ; side view showing wall of parent colony, 



adjacent somatic cells and older embryo slightly out of focus (685). 

 A x 70. B x 45. C to E x 25. F x 390. 



PLATE XXVII. 

 Volvox gigus. Inversion of embryo. 



A. Phialopore wide open, lips nearly straight ; protoplasmic connections between 

 the cells at the edge of the lip were clearly visible (689). 



