Volvox in South Africa. 565 



2. F. capensis. In V. capensis, however, as in V. globator, the 

 sexual colonies are monoecious and strongly protandrous. If mature 

 sexual colonies are under examination they appear purely female, 

 containing only oospores (Plate XIII, E). But small, fairly regular 

 gaps in the cell network are invariably present, indicating the positions 

 where sperm globoids have matured and escaped. Only very rarely 

 are sperm globoids seen in a colony with well-developed oospheres. 

 Usually they are seen in young colonies only, where the oospheres 

 are still in the stage of enlargement (Plate XIII, C) and not nearly 

 ready for fertilisation. 



As in the case of the daughter colonies, the male globoids seem 

 often to average 8, arranged similarly in two planes, but in addition 

 to these 8 primary male cells there are often considerably more in 

 the colony. The total number varies greatly and it is difficult to 

 fix the minimum, since here, too, some may have escaped before some 

 of the others, even of the primary 8, have developed. Colonies 

 with 2 or 3 sperm globoids only have been seen, but gaps in the 

 cell network showed that more had been formed. The following 

 observations give some indication of the variation in numbers : 



(1) Of 19 colonies examined at various times from Ottery Road, 

 10 had 8 male globoids, 4 had 10, 2 had 9, 2 had 5 but in one of 

 these a gap was seen, 1 had 4 but showed 3 gaps. 



(2) In the Belvedere Eoad Vlei III towards the end of the 1931 

 season the number of sperm bundles was high ; 8 was still a common 

 number, but colonies with 12, 13, and as many as 19 were found. 



(3) In the material from N. Rhodesia the number of globoids is 

 usually high, much higher than has ever been observed at the Cape, 

 as many as 35 having been counted in a single colony. 



When more than 8 globoids are formed, the arrangement in two 

 planes becomes obscured, the extra androgonidia being scattered 

 about among the young oospheres, although usually the positions 

 of the original 8 can be traced. 



As in the case of the asexual daughters, there is some evidence to 

 indicate that the number of sperm globoids is influenced by external 

 conditions, particularly temperature. 



C. The Female Initial Cell, Oogonium Mother-cell, or Gijno- 



gonidium. 



1. V. Rousseletii. The female initial cells occur in the posterior 

 two-thirds to three-quarters of the female colony and are generally 

 numerous, the majority coming to maturity as spiny-coated oospores. 



