612 Annals of the South African Museum, 



over practically the whole area Volvox was soon abundant, the 

 colonies being exceptionally large for this species. Obviously the 

 oospores had retained their viability for three and four years respec- 

 tively. That the spiny outer coat is an excellent protection against 

 attack by small animal organisms became very apparent in the 

 oospore culture experiments described below while the smooth, 

 round spores after escape from the spiny coat were repeatedly seen 

 in the alimentary canals of Paramoecium and various small worms, 

 complete spores were never so observed. 



Subsequent Development of the Oospore in V. Rousseletii and 



V. capensis. 



When one considers that the average adult colony in either of these 

 two species contains between 20 and 30 thousand cells, the product 

 of some 14 or 15 successive cell-divisions, that the oospore, including 

 the spiny covering, measures only some 50 to 60 /z, and the actual 

 spore-protoplast only about 44 JJL, that the spore is free in the soil at 

 the bottom of the water and must contain sufficient food stored within 

 it to carry the young colony through all the stages of cell-division and 

 subsequent development, until it reaches the motile state, it seems 

 difficult to conceive of such a colony being produced directly from 

 division of the oospore. Apart from the question of size, the risk 

 of injury or destruction would be enormously increased if develop- 

 ment were prolonged. Evidently the germination processes must 

 be rapid, for within 4 or 5 days of the forming of a pool, well-developed 

 Volvox colonies may be found. 



Discovery of the Juvenile Form. 



In May 1931 at the beginning of the month there were several 

 showers, sufficient to moisten the earth on the Cape Flats but not to 

 form pools. About llth May further rain fell, and pools formed on 

 the grassy common which is bounded on two sides by Belvedere 

 and Keurboom Eoads. Near Keurboom Road one elongated de- 

 pression annually forms a pretty little vlei,* usually producing much 

 Volvox. On 15th May this was visited and found to contain a small 

 pool of water. The use of the collecting net revealed the presence 

 of fair-sized colonies of Volvox and also, particularly from one spot, 



* Unfortunately soon to be a thing of the past, as it lies within the boundaries 

 of what is now Ackerman's Sports ground, and is being filled in. 



