614 Annals of the South African Museum. 



is a deep golden brown, and if it has been dried the protoplast 

 enclosed in the delicate endospore is usually contracted away from 

 the mesospore and often placed somewhat eccentrically in it, sepa- 

 rated from it by a clear space. 



A more or less prolonged resting period may intervene before 

 germination, or the oospore may germinate immediately. Here 

 external conditions appear to be of paramount importance, always 

 allowing, however, for some individual idiosyncrasy of the oospores. 

 During the resting period no further change takes place in the appear- 

 ance of the oospores. 



Collection of Oospores. 



For obtaining ripe oospores for germination experiments, V. 

 Rousseletii affords extremely favourable material not only does it 

 contain more oospores per colony than V. capensis but female 

 colonies are produced in larger numbers and retain the ripening 

 oospores to an advanced stage before disintegrating. In February 

 1931 Mr. Steer's Eietfontein cultures provided particularly rich sexual 

 material in an advanced stage of development, hence with abundance 

 of ripe or nearly ripe oospores. A quantity of this material was placed 

 in an old glass battery jar 5 inches square, half filled with water. As 

 the female colonies ripened and disintegrated, the oospores collected 

 at the bottom of the jar as a red-brown sediment ; the bulk of the 

 soft part of the detritus was consumed by various organisms, chiefly 

 rotifers and Paramoecium. The spiny coats of the oospores evidently 

 form an efficient protection, since complete oospores were never seen 

 inside these voracious little creatures, whereas after germination 

 had begun and the spore enclosed in the smooth inner wall had escaped 

 from the spiny covering, the still undigested red-brown spores were 

 frequently seen in the digestive organs, of Paramoecium in particular. 



On 17th February some of the oospore sediment was placed on 

 slides and put aside to dry. The rest was left untouched for some 

 months. The jar stood near a window with a southern aspect, so 

 that, though well lighted, direct sunlight never fell on it. The water 

 gradually evaporated, but was never allowed to dry up completely. 



Culture Methods. 



Nothing further was done in the matter until the end of June ; 

 then germination experiments were started and carried on through 

 July and August, when the supply of material was exhausted. These 

 experiments were of four main types, and in each case both material 



