438 Annals of the South African Museum. 



characters in common with V. globator, and that it is intermediate 

 between that species and V . Rousseletii. 



Before proceeding to describe the forms we have found, we think 

 it advisable to enumerate the features on which Shaw laid stress in 

 describing new species and genera from Manila.* In addition to 

 the recognised significance of dimensions, presence or absence of 

 connecting protoplasmic strands, and variations in the oospore wall, 

 he considered of importance the size attained by the gonidia (the 

 asexual reproductive cells) before dividing, and whether or not they 

 become segmented before the birth of the young coenobia in which 

 they occur. Another point of importance, in his view, is whether 

 all the daughter colonies are born through one opening in the wall 

 of the mother colony, or whether each daughter is born through a 

 separate opening ; a study of this in preserved material is, of course, 

 very unsatisfactory. Shaw also laid stress on the migration of the 

 gonidia from the outside to the inside of the developing embryo, but 

 the subsequent or almost simultaneous work of Kuschakewitsch j- 

 has shown that on completion of cell-division of the developing 

 gonidium the young coenobium (embryo) undergoes complete inver- 

 sion, whereby the inner surface comes to lie outside. J Shaw further 

 pointed out that it was important to make observations during the 

 night or late afternoon, when he believed many of the changes in the 

 life-history usually occur. We have acted on this hint, but so far 

 our results do not confirm Shaw's opinion it is possibly correct as 

 regards actual cell-division, but all other stages have been observed 

 during the day as well as at night ; in fact, inversion appears to take 

 place more commonly during the day, which perhaps explains how it 

 came about that Shaw during his extensive studies on Volvox over- 

 looked this phenomenon. 



In the following account we deal with the forms of Volvox we have 

 examined from different localities, placing each under the species to 

 which it belongs. 



* Shaw, W. R., op. cil., vol. xv, 1919 ; vol. xx, 1922 ; vol. xxi, 1922 ; vol. xxii, 

 1923. 



f Kuschakewitsch, Bull. Acad. Sc. de 1'Oukraine, vol. i, 1922, p. 1. 



J Both Kuschakewitsch and Zimmermann (Naturwissenschaften, 1925, p. 401) 

 thought that inversion preceded cilia formation. Recent observations of the South 

 African forms, however, show that the cilia are being formed during the process, 

 and that probably the mechanism of inversion is intimately connected with cilia 

 formation. 



