Volvox in South Africa. 525 



INTRODUCTORY. 



FROM the time when Volvox was first observed and described by 

 Leeuwenhoek (1719, p. 149) it has been a favourite object for micro- 

 scopic study, and there has sprung up an extensive literature on the 

 genus Volvox, fruit of the labours of both botanists and zoologists 

 as well as microscopists. 



Nevertheless, even in such well-known forms as Volvox globator (L.) 

 Ehren. and Volvox aureus Ehren. ( = Janetosphaera aurea Shaw) 

 certain points in the life-history remain obscure. Pascher (1927, 

 p. 450, note) points out that his account of the genus can only be 

 regarded as provisional owing to the lack of comparative studies 

 from wide areas. Again, he emphasises the need for further investi- 

 gation by means of careful fixation, sectioning, etc., but above all 

 for numerous studies of living material. 



That there has been a tendency to neglect the latter is well exem- 

 plified by the fact that the inversion of daughter colonies subsequent 

 to the last cell division in the development of the gonidium was 

 accurately described for the first time as recently as 1919 by 

 Kuschakewitsch (1922), although it had actually been observed by 

 Powers years earlier (1908, p. 158), and this despite the fact that if 

 a small quantity of a well-developed, actively reproducing gathering 

 of Volvox is placed in a watch-glass of water and observed for half 

 an hour or so under a low power of the microscope, some of the 

 daughter colonies are almost certain to show inversion, in living 

 material a most striking and very easily observed phenomenon. 

 In his critique of Kuschakewitsch's paper, Zimmermann (1923, p. 85) 

 remarks : ' The discovery (i.e. of inversion) shows perhaps even more 

 markedly than the discovery of the gametophyte generation in 

 Laminariaceae how fundamentally wrong it is to assume, even in 

 such fully investigated organisms as Volvox, that the earlier in- 

 vestigators fully elucidated all points, even if only in the external 

 course of development." 



Volvox has been known from Rhodesia since 1905 (Rousselet, 

 1906, p. 393 ; and West, 1910, p. 99), from the Cape Flats from about 

 1915, and more recently from various other localities in South Africa. 

 Little has, however, been done on the South African forms beyond 

 describing them generally (as a rule from preserved material only) 

 and recording their occurrence. No systematic observations of the 

 behaviour and development of Volvox in this country have been 



