446 Annals of the South African Museum. 



The daughter colony rotates for some time within its vesicle (the 

 enlarged gonidium wall), finally escaping outwards through a pore 

 which it bores in the wall of the coenobium. Normally, in a healthy 

 colony each daughter escapes thus through its own pore ; the daughter 

 colonies do not rotate freely within the hollow of the parent ; each 

 vesicle remains intact until broken by the escaping daughters in the 

 region where it forms part of the outer membrane of the colony. 



The sexual colonies are usually globose (Plate XIII, fig. C) or 

 broadly ellipsoidal, somewhat smaller than the asexual colonies, 

 monoecious and strongly protandrous, with well-marked polarity, 

 the anterior end always being clear of reproductive cells. Unless the 

 strain is an old one nearing the end of sexual activity it is most 

 unusual to find daughter colonies in a sexual coenobium. The 

 antheridia vary from about 4 to 20 in number, usually from about 

 6 to 10. As in the case of the gonidia, there appear to be 8 primary 

 antheridia arranged similarly, i.e. alternately in two planes. More 

 than 13 were found only in the hot weather form from Belvedere Road. 

 The mature sperm bundle is a depressed hollow globoid of 512 sper- 

 matozoids, the central hollow appearing circular in surface view, 

 narrowly elliptical in side view (Plate XV, figs. C and D). The cilia 

 are very long. Like the daughter colony, the sperm globoid usually 

 escapes outwards ; occasionally, however, it escapes inwards, and 

 may disintegrate within the hollow of the parent. The spermatozoid 

 is similar to that of V. Rousseletii (text-fig. 3, D). 



When the sperm globoids are fully developed, the oospheres are 

 still immature ; only very rarely are sperm globoids and oospores to 

 be found in the same colony. Gaps in the cell network show where 

 the globoids have developed and escaped (Plate XIII, fig. C). 



The oosphere (Plate XII, fig. E) is deep green, very broadly flask- 

 shaped, the broad apex a little below the outer surface of the parent. 

 After fertilisation it rounds off, lying below the level of the inner 

 membrane, enclosed within the delicate vesicle formed from the much 

 enlarged wall of the oogonium, which in its early stages develops 

 similarly to the young antheridium. Within this vesicle the oospore 

 develops. At first it is bounded by a thin wall ; the outline becomes 

 irregular, and an outer hyaline wall of spirally arranged conical spines 

 is formed, the green protoplast extending into the spines. When this 

 exospore has been secreted, the green protoplast is withdrawn from 

 the spines, rounds off once more, and the inner wall is laid down (text- 

 fig. 4, C, and Plate XV, fig. F). This again consists of two layers a 

 thick mesospore and a very delicate endospore bounding the protoplast. 



