Volvox and Associated Algae from Kimberley. 489 



V. Rousseletti, in which closure has not been complete and which have 

 not yet undergone subsequent compression (fig. 3, H, J, and Plate 

 XXIX, E). In side view such bundles, like the smaller ones, are bowl- 

 shaped, almost globular, but flattened at the open side. Thus in one 

 and the same colony sperm bundles of several different sizes may 

 occur' (Plates XXIX, A, C, and XXX, A). 



Stages in the development of sperm bundles are shown in fig. 3. 

 Division of the antheridium mother-cell (fig. 3, A, B) follows the 

 usual lines, resulting in the formation of a more or less rounded hollow 

 bowl or globe according to the number of divisions undergone ; where 

 the divisions are few the resultant structure is more open and bowl- 

 shaped, or, even in the case of the smallest bundles, saucer-shaped, 

 while the very large type is almost globular (fig. 3, C). On completion 

 of cell division inversion takes place ; although few stages could be 

 made out, sufficient were seen to indicate the type of inversion. In 

 the case of the smaller bundles it is similar to that seen in Eudorina, 

 while in the larger, many-celled bundles it is naturally rather more 

 elaborate, approaching that seen in the case of the asexually formed 

 embryos. Fig. 3, D, shows a medium-sized bundle in which the 

 phialopore is opening preparatory to inversion, while fig. 3, E, shows a 

 recently inverted small bundle with elongating cilia. Fig. 3, F and G, 

 show optical sections of bundles of 64 and 128 spermatozoids re- 

 spectively, while the largest-sized bundles are shown in different views 

 in fig. 3, H and J. An early stage in the development of such a 

 bundle is shown in Plate XXIX, fig. B, in which the second cell 

 division is not quite complete ; the separation of the cell apices is 

 particularly clear, while the surrounding vesicle is faintly discernible. 

 The adjoining microphotograph (E) shows the appearance of the 

 mature bundle. 



Examples of male colonies are illustrated on Plate XXVIII. Of 

 the four male colonies depicted, one (C) contains only small and 

 medium-sized sperm bundles, while the other three all contain a 

 number of the largest sized as well. These appear in the photographs 

 as very dark, rounded bodies. Of the smaller bundles many are in 

 early stages of division, others are inverting. Colonies A, B and C 

 are of the characteristic egg-shape ; D is more nearly spherical. 

 Plate XXIX, figs. A, C, and D, show portions of male colonies further 

 enlarged to show details of structure and development of sperm 

 bundles of various sizes. 



The spermatozoids (fig. 3, K) are found in great numbers swarming 

 on or within the peripheral layer of colonies containing oospheres 



VOL. XVI, PART 3. 32 



