480 Annals of the South African Museum. 



II. Genus VOLVOX (Linnaeus) Ehrenberg. 



Section MERRILLOSPHAERA (Shaw) Printz. 



1. Volvox gigas sp. nov. 



(Text-figures 1-3, Plates XXV-XXX.) 



Volvox maximus, coenobiis asexualibus mixtisque sub-globosis, 

 usque ad circa 3 mm. latis ; cellulis rotundis, circa 1000-3000, sine 

 connexionibus ; coenobiis infantibus permultis usque ad ca. 82, 

 plerumque 30-60, interdurn cum numerosis oosporis mixtis ; coeno- 

 biis prorsus sexualibus minoribus quam asexualibus vel mixtis ; 

 coenobiis masculis oviformibus usque ad circa 1 mm. latis, 1-3 mm. 

 longis, vel rotundis, minoribus ; antheridiis numerosis usque ad 

 circa 600-700 in parte quarta anteriore absentibus, spermatozoidis 

 longis, 16,32,64, vel 256,512 coalitis in globulis 18-22 p,, vel 40-49 p, 

 latis ; coenobiis fernineis globosis usque ad 2-25 mm. latis, oosporis 

 numerosis, globosis, membrana duplici, episporio levi, aliquanto 

 crassi, endosporio tenue. 



Coen. asex. et mix. . . 1615-2800 p. x 1700-3135 p, 



Coen. masc. . . . 732-1141 ^ x 797-1292 /x 



Coen. masc. min. . . 246- ? fix 242- ? p, 



Coen. fern. . . 1679-2154 p. x 1723-2206 p. 



Coen. infant. . . . 108-388 p, x 129-431 p. 



Cell. veg. . . 26-84 p. 



Pplast. veg. . . . 9-13 /x; Stigma, 3-4 p, 



Goniclium . . . 35-49 p, 



Glob, sperm. . . . 18-22^; vel 40-49 /x 



Spermatozoid. . . 2-4 p, x 11-17 p.; cilia, 14-19 p, 



Cell. num. . . 1000-3000 



Coen. infant, num. . . ad 82 ; pier. 30-60 



Glob, sperm, num. . . ad ca. 600 vel 700 



Oospor. num. . . ad ca. 300 vel 400 (?) 



Found in Pool I only. 



This remarkable member of the Volvox group is outstanding on 

 account of : (1) its size, completely dwarfing the form of V. Rousseletii 

 a fairly large one with which it is associated ; (2) the large number 

 of daughter colonies, as many as 82 having been counted in one 

 coenobium, while 30 to 60 per coenobium, often associated with 

 numerous oospores, are common ; (3) the slow development ; the 



