I'.M 



Annals of the South African Museum. 



The species is very distinctive, in some ways the most beautiful 

 of all the African species of Volvox (Plate XXXI, A-D). Its fairly 

 large ellipsoidal colonies with symmetrically arranged pairs of embryo 

 colonies are quite unmistakable, even in the absence of sexual 

 reproductive organs. The two poles are usually equally rounded, 

 though occasionally one, usually the anterior, but sometimes the 

 posterior pole, may become slightly broader than the other. 



The Kimberley material includes colonies considerably larger 

 than any yet described, and, in spite of its rarity, there was sufficient 

 material to add several details to our knowledge of the species. It 

 is therefore described here in some detail. 



Membranes. Diagrams showing the form of the membranes in 

 this species have already been published (Rich and Pocock, loc. cit., 



B 



FIG. 4. V. africanus, treated with dilute methylene blue to show the 



membranes. 



A, Young colony, optical section, polar view ; B, older colony after escape of 

 equatorial embryos. Side view. x about 45. 



p. 432, fig. 1, B). As, however, no detailed description of them was 

 given they are briefly described here. 



As in Volvox gigas and Volvox tertius, each cell is enclosed in a 

 lenticular membrane which is united with the outer common envelope 

 above the protoplast. The adjacent cell membranes are often sepa- 

 rated from one another, but never to so great an extent as in the 

 mature colonies of V. gigas. 



The inner limiting membrane is fairly distinct and regular in young 

 coenobia, the developing embryos in their surrounding vesicles lying 

 in the peripheral layer between the inner and outer membranes 

 (fig. 4, A). As the embryos develop, however, they grow very large 

 and push aside the inner membrane, displacing it considerably 



