Observations on the Genus Volvox in Africa. 433 



by a flat wall, and the cavity of the coenobium within the layer of cells 

 is occupied, according to Meyer, by a watery fluid. It will thus be 

 seen that the differences between these two are greater than is usually 

 the case between two species of the same genus, and it is not surprising 

 that the suggestion has been made that they should be separated. In 

 1922 Shaw * placed F. aureus in a new genus which he named Janeto- 

 sphaera, retaining F. globator in the genus Volvox, while he placed 

 F. tertius, in which there are no protoplasmic connections between the 

 protoplasts, in another distinct genus Merrillosphaera. 



Of these, Volvox is represented in Africa by several species, of which 

 F. Rousseletii is widespread ; the present paper describes further species 

 and forms belonging to this section. Janetosphaera is represented by 

 J. aurea ( = V. aureus), differing in no marked degree from that found 

 in Europe, while F. africanus belongs to the third section ( = Merrillo- 

 sphaera africana, according to Shaw). 



None of the recently published comprehensive accounts, however, 

 has adopted Shaw's nomenclature, hence the present writers are not 

 using it. All who have worked at the group agree that a revision is 

 necessary, cf. Pascher f and Printz.J The latter divides the genus 

 Volvox into subsections, to which he applies Shaw's generic names. 



G. S. West considered that F. africanus was the African species 

 comparable with the European F. aureus, and that F. Rousseletii was 

 similarly comparable with F. globator. The present authors feel 

 that the resemblance between the two latter is greater than that 

 between F. africanus and F. aureus. Moreover, F. aureus itself 

 occurs extensively in Africa. F. africanus is more nearly com- 

 parable with the European species F. tertius Meyer, its membranes 

 being similarly constructed to those of the latter (see text-fig. 1, B). 

 The features on which West based his two African species may 

 be usefully enumerated here as follows : 



Volvox africanus : 



1. The coenobia, though approximately the same size as those of 

 F. aureus, are of a different shape, being constantly ovoid or egg-shaped. 



2. The constituent cells number from 3000 to 8000. 



3. The daughter colonies vary in number from 1 to 4 (3 is a common 

 number). 



* Shaw, W. R., The Philippine Journ. of Sci., vol. xx, 1922, p. 478. 

 t Pascher in Die Siisswasserflora Deutschlands, Osterreichs und der Schweiz, 

 vol. iv, 1927, p. 462. 



J Printz, Volvocaceae in Engler's Nat. Pfl. fain. Ed. II, vol. iii, 1927, p. 59. 

 West, G. S., op. cit., 1918, p. 426. 



