Volvox in South Africa. 571 



(fig. 2, K, L ; Plate XL, A), and may be either quadrilateral or tri- 

 angular in shape, in V. capensis more often the latter. The two shapes 

 may occur side by side in young daughters of the same parent. 



Microtomed sections of the developing daughter show the cells 

 as broadly wedge-shaped, the broad chloroplast-containing base 

 directed outwards, the roundly pointed colourless apex towards 

 which the nucleus lies directed inwards. 



When the development and structure of the gonidium is compared 

 with the accounts given in the cases of F. aureus and V. globator by 

 Janet and others the following points emerge : 



(1) The shape of the gonidium prior to the first division differs from 

 that in V. aureus, where it is described as almost spherical (Janet, 

 1923, p. 109). 



(2) The number of successive divisions is in general greater than in 

 F. globator and much greater than in F. aureus. 



(3) The phialopore or ostiole always lies symmetrically beneath 

 the area of attachment to the parent, and the protoplasmic strands 

 connecting daughter to parent are attached in a ring round the phialo- 

 pore, but in later stages of division not to the cells immediately abutting 

 on the pore. Several rows of cells form a free rim to the pore within 

 the connecting strands (fig. 2, J, K). 



(4) The connections between mother and daughter remain intact 

 till a much later stage in development. 



In F. globator, wherever the attachment of daughter colony to 

 parent is shown, the protoplasmic strands are always depicted as 

 attached to the cells immediately round the pore (cf. Janet (1912, 

 p. 35, fig. 1), Zimmermann (1925, p. 399, fig. 1)). Possibly it is a detail 

 of structure which has escaped notice in that species ; the preserved 

 material of F. globator available for comparison is not sufficiently 

 well preserved to show the mode of attachment of the embryo. 



3. Period of re-orientation -Inversion. How long an interval, if 

 any, elapses between the completion of the last cell-division in the 

 daughter colony and the initiation of the changes that lead to the 

 eventual re-orientation of the cells composing it has not yet been 

 determined. It is probably short. 



The process of inversion is essentially similar in F. Rousseletti 

 and F. capensis ; variations were noticed, and it was thought that 

 there might be specific differences, but further observations showed 

 that these are not constant specifically but are differences in behaviour 

 of individual daughters. 



The process falls into two well-marked stages, the second only 



