The Rotifer a of South Africa. By Charles F. Rousselet. 409 



The subjoined list of all South African Eotifers, as far as known 

 at present, contains 156 species. Their distribution in the various 

 Colonies is as follows : Cape Colony, 91 species ; Orange Kiver 

 Colony, 12 species ; Transvaal, 9 species ; Natal, 73 species ; 

 Ehodesia, 54 species. 



Mr. Wm, Milne's list for the Uitenhage district of Cape Colony 

 is shown in a separate column, 2. 



In glancing over this list, one cannot but be struck with the 

 remarkable world-wide distribution of so many of these minute, 

 but highly organised, creatures, with identical shapes, markings, 

 spines, and other features. The best explanation is that the 

 Eotifera, in addition to thin-shelled summer eggs which hatch at 

 once, produce resting eggs with thick, tough shells, capable of with- 

 standing any amount of desiccation, and which may be wafted up 

 with the dust of dried-up pools, and carried very long distances by 

 the wind and air currents, and thus scattered over the whole 

 surface of the earth, and then come to life and reproduce their kind 

 whenever they happen to fall on a spot suitable for their existence. 

 There are, no doubt, other modes of distribution, such as the agency 

 of aquatic birds, but the above, I think, is the principal one, and 

 the only one that can satisfactorily account for the existence of so 

 many identical species in Europe, America, China, India, Australia, 

 and Africa. 



This list of South African Eotifers is also remarkable for the 

 total absence of a few prominent groups, such, for instance, as the 

 Asplanchnas, which are very abundant in many places in Europe, 

 and being large and readily captured with other plankton, could 

 not be missed if present. 



Then the case of Anurcea aculeata is most peculiar. This is a 

 very common, and often enormously abundant, species in Europe 

 and other countries, but in South Africa I did not come across it 

 once, although the closely allied variety " valga," which differs 

 only in having a shorter posterior spine on the left side, is present 

 in nearly all my collections in the Orange Eiver Colony and 

 Ehodesia. 



I may add here that on the way out, from Madeira to Capetown, 

 and also on the East Coast from Beira to Suez and Marseilles, I 

 made daily collections of plankton from the sea by allowing the 

 water, which is pumped up every morning for the purpose of 

 washing the decks and delivered by the hose, to run through my 

 net for about an hour. In this way I obtained an abundance of 

 living marine creatures, mostly Infusoria, Copepods, larval worms, 

 diatoms, etc., but only once did I find a Eotifer, namely, Synchwta 

 vorax Eouss., in the Bitter Lake of the Suez Canal. 



Aug. 15th, 1906 2 e 



