G. S. WEST OX SOME NEW AFRICAN SPECIES OF FOLVOX. 101 



fully distinct. In this species there are no connecting strands 

 between the cells of the adult colony. 



Quite recently two papers on American species of Volvox have 

 appeared by J. H. Powers,* in which the author describes 

 several new forms under the names of V. spermatosphaera^ 

 V. Weismannia, and V. jjerglobator. The distinctions drawn up 

 by Powers are concerned principally with the development of the 

 reproductive colonies and the reproductive cells. He thinks it 

 likely that the European species do not exist in America, and 

 that the American species of Volvox are distinct races. 



Volvox Rousseleti, sp. nov. 

 (PI. 3, Figs. 1-7.) 



In September 1905, at the time of the British Association's 

 visit to South Africa, Mr. Bousselet collected from a pool near 

 the station at Gwaai in Rhodesia a truly remarkable species of 

 Volvox. All the specimens sent me for examination were purely 

 vegetative. Yet, notwithstanding the entire lack of knowledge 

 of the sexual colonies, I have no hesitation in regarding these 

 specimens as vegetative (or asexual) colonies of a new species of 

 the genus. 



The adult colonies are large and globose, measuring 1,1 25-1, 240/x 

 in diameter. In appearance they are very robust, much more 

 so than those of any other species of Volvox, a feature which is 

 due to the dense crowding of the constituent cells. The number 

 of cells in the colony could be very easily estimated, and was 

 found to vary from about 25,000 to rather more than 50,000. 

 It is this enormous number of cells constituting the colony, and 

 the density of their arrangement, which form the diagnostic 

 features of this large African species. 



The cells are 4-6 '5/x in diameter, and are separated by 

 intervening spaces of less than their own breadth. In surface 

 view (vide Fig. 7) they are seen to be somewhat angular, and in 

 all the specimens they appeared to possess relatively stout proto- 

 plasmic connecting processes. I say " appeared to possess " 

 because it is unsafe to give a decided opinion on this point unless 

 the colonies have been fixed with the greatest care. 



The number of daughter-colonies produced by one individual 



* J. H. Powers in Trans. Amev. Jlicroscojj. Soc, xxvii., 1905; xxviii., 1906. 



