Volvox in South Africa. 635 



in the group, wherever a single reproductive cell divides to form a 

 spherical bundle of cells. In every case the cilia are formed during, 

 and not subsequent to, the process of inversion. The emission of the 

 cilia plays an important part in bringing about inversion. 



The changes brought about by varying conditions and ageing of 

 the strain are indicated, and the great variability of the members 

 of the group illustrated by the behaviour of the two species. 



The existing classification of the group can only be regarded as 

 provisional, but before a detailed revision can be attempted extensive 

 observations of and experiments with living material of the various 

 species are necessary. 



The above in the main formed the subject of a thesis submitted 

 in March 1932 for the degree of Ph.D. of the University of Cape 

 Town. The thanks of the author are due to Mr. E. J. Steer, not only 

 for an unfailing supply of material, but also for the use of certain 

 pieces of apparatus, to Professor Fritsch and Miss F. Rich of the 

 East London College, University of London, and to various members 

 of this university: to the Librarian and staff of the Jagger Memorial 

 Library for facilities accorded while consulting various works bearing 

 on the subject, to Miss E. L. Stephens for the use of her collection of 

 Algal literature, to Mrs. Levyns and to Professor Adamson, Harry 

 Bolus Professor of Botany, for much helpful criticism and encourage- 

 ment during the course of the investigation. 



DEPARTMENT OF BOTANY, 



UNIVERSITY OF CAPE TOWN, 



December 1932. 



