425 



A FURTHER CONTRIBUTION TO OUR KNOWLEDGE 

 OF THE TWO AFRICAN SPECIES OF VOLVOX. 



By G. S. West, M.A., D.Sc, F.L.S., 



Mason Professor of Botany in the University of Birmingham. 



{Read April dth, 1918.) 



Plates 29 and 30. 



Some few years ago the author published a paper * on " Some 

 New African Species of Volvox," described at that time exchi- 

 sively from vegetative individuals. One of these, Volvox Rousse- 

 letii, is the largest known species of the genus and was obtained 

 by Mr. Rousselet from a pool near Gwaai in Rhodesia in September, 

 1905 ; the other species, F. ajricanus, was collected by Mr. R. T. 

 Leiper in Uganda in July 1907. 



Since then Mr. Rousselet has obtained some plankton-material 

 collected by Dr. Jakubski of Lemberg (Lwow) from small tem- 

 porary pools in the Ussangu Desert in the African region formerly 

 known as "German East Africa," and in this materialwere present 

 sexual colonies of the above-mentioned African species of Volvox. 



Although the vegetative characters were amply sufficient tO' 

 establish these two species, great interest is naturally attached to 

 the discovery of their sexual colonies, since it assists in completing 

 the description of these African types of Volvox and shows still 

 more clearly that they are distinct races as compared with the 

 European types. 



Mr. Rousselet has published a preliminary note f stating how 

 he obtained these sexual colonies in 1914 and that they had been 

 submitted to me for detailed investigation. 



The sexual colonies have been photographed and a selection of 

 these photographs appear on the accompanying plates. Unfor- 

 tunately, no male colonies of V. africanus were found in this East 



* G. S. West in Journ. Quek. Micr. Club, ser. 2, vol. xi., Nov. 1910, 

 pp. 99-104. 



t C. F. Rousselet in Journ, Quek. Micr. Club, ser. 2, vol. xii., Nov. 

 1914, pp. 393-394. 



