Observations on the Genus Volvox in Africa. 459 



Mature daughter colony, 182x204 p to 630x672 /x; average 



diameter 300 to 400 /*. 



Somatic cell : anterior pole 11 to 17 /x ; posterior pole 6 to 11 JJL. 

 Somatic protoplast : anterior pole 5 to 8 /z ; posterior pole 3 



tO 6 fJL. 



Somatic protoplast in daughter colony at birth, 4 to 6 /z. 

 Gonidium protoplast in daughter colony at birth, 13 to 15 /u,. 

 Number of somatic cells, 14,000 to 42,000; average 20,000 to 



23,000. 



Number of daughter colonies, 1 to 16, usually 6 to 10. 

 Number of sperm globoids, 108 to 214, probably more. 

 Number of oospores, 60 to 201 ; average 160 to 170. 

 Size of sperm globoid, 35 to 43 (j,. 

 Size of oospore with spines, 44 to 59 jit ; without spines, 35 to 44 /z ; 



spines, 5 to 10 /a. 



4. From Eliazer Pan (Potchefstroom) and Brakpan, both in the 



Transvaal. 



At Potchefstroom a similar Volvox with both male and female 

 colonies was found associated with V. aureus (Plate IX, fig. A). From 

 Brakpan no sexual colonies were obtained. 



5. From Sedudu, Linyanti River, Bechuanaland Protectorate. 



In most of the vleis, etc., examined in this district the monoe- 

 cious V. capensis was present. At Sedudu, however, in a small pan 

 V. Rousseletii with typical male colonies containing numerous an- 

 theridia (between 200 and 300) was found (Plate XXII, fig. A) 

 associated with ovoid asexual colonies ; the cell network appears 

 finer than in V. capensis. V. Rousseletii was also found in some of 

 the backwaters of the Linyanti River itself. 



6. From Grahamstown, Cape Province. (Collected by Miss L. Britten.) 

 The material was nearly all asexual, somewhat badly attacked by 



Rotifers. From the ovoid form of the large asexual colonies, and from 

 the single young sexual colony with large oospheres and no sign of male 

 elements, this Volvox is probably V. Rousseletii, but further sexual 

 material is necessary before it can be fully identified. The asexual 

 colonies are large of those measured, all immature, the dimensions 

 ranged from 948 x 990 /j, to 1120 x 1184 /z, with from 8 to 12 daughters, 

 of which most had still not inverted. The single sexual colony 

 measure 495 x 559 fi, and contained about 40 large bodies, apparently 

 eggs which had rounded off but had not yet laid down their walls. 

 VOL. xvi, PART 3. 30 



