Observations on the Genus Volvox in Africa. 443 



1. From the Cape Flats. 



The " Cape Flats " is the name given to the strip of low-lying land 

 forming the isthmus which joins the Cape Peninsula to the mainland. 

 The greater part is covered by blown sand, but near Table Mountain 

 are fairly extensive stretches of alluvial soil (Plate XXIV, fig. D). 

 During the winter months shallow pools, some of considerable extent, 

 form on the flats, and these yield a rich algal flora. In several of 

 those on the alluvial soil Volvox has been found ; all dry up very soon 

 after the south-east winds of early summer begin, so that as a rule 

 Volvox is found only in winter and spring, only very rarely is it 

 found as late as November, as in 1931. 



In October 1927 Volvox was collected from two of a series of vleis 

 near Belvedere Road * (between Keurboom and St. Michael Roads), 

 Claremont, and from Scanlan's Vlei, Wetton Road, a few miles 

 distant ; observations were started on the living material, but the 

 supply ran short just when further investigations were desired. The 

 following season (1928) was a particularly good one for Volvox, whereas 

 that of 1929 was very unfavourable the winter rains accompanied 

 by cold weather were late, the late rains were poor, and many 

 vleis did not fill up at all. At first a fair amount of good Volvox 

 material (all asexual) was collected, but later on in the season repeated 

 efforts to obtain sexual material were entirely unsuccessful. In one 

 case a promising pool in a ditch near the farm Vaderlandsche Rietvlei 

 yielded on a second visit plenty of coenobia, but in every case they 

 were inhabited by a Rotifer busily eating away daughter colonies and 

 parent cells,f and no sexual colonies were present (Plate XIV, figs. 

 B-D). Other pools previously full of Volvox had now scarcely any 

 water in them and consequently no algal growth. 



The winter of 1930 was exceptionally dry, particularly on the Cape 

 Flats one farm on Princess Vlei recorded a total rainfall of only 4 

 inches for the year (considerably less than the Kalahari) and in most 

 parts the rain simply soaked into the ground, no pools being formed. 

 The Wetton Road Vlei, however, was an exception to the general rule ; 



* Of these, one of the best has since become part of Ackerman's Sports Ground, 

 and is in process of being filled up with rubbish and sand. 



t A photograph of this Rotifer has been sent to Mr. C. C. A. Monro, Assistant 

 Keeper in the Department of Zoology, British Museum (Natural History), who 

 has been kind enough to examine it. He says the photograph appears to corre- 

 spond most nearly to Ascomorpha volvocicola Plate. Several species of Rotifer are 

 known to live in Volvox. Many individuals and their eggs were often observed 

 inside a single coenobium. Even when half the cells and the daughter colonies 

 had been devoured the colonies were still active and strongly phototactic. 

 VOL. XVI, PART 3. 29 



