304 Annals of fJ/f- Houfh African, Museum. 



said method has proved to be of invaluable service, as these very 

 delicate organisms scarcely admit of being satisfactorily examined 

 except in the fresh and living condition. By immersion in alcohol or 

 any other preserving fluid, they very soon not only lose much of their 

 beauty and transparency, but in many cases even become more or less 

 deformed by the contraction of the softer parts and the inconvenient 

 twisting of the natatory antennae and the caudal part, so as to be less 

 serviceable for an exact examination. The imperfectness of the habitus- 

 figures generally given of exotic Cladocera is indeed in most cases due 

 to the above-mentioned injurious action of the preserving fluid on the 

 specimens examined. 



The mud which has been placed at my disposal was taken from four 

 different localities in Cape Colony, viz. : 



(1) Knysna. Four parcels collected by Mr. Theson from a swamp 

 in 1890 and 1891. 



(2) Port Elizabeth. Three parcels kindly forwarded to me in 1897, 

 1899 and 1900 by Mr. Hodgson, and collected by his brother from a 

 " vley" near that town. 



(3) Green Point Common. Several small parcels kindly sent to me 

 in 1898 and 1899 by Dr. Purcell. 



(4) Cape Flats and neighbourhood of Bergvliet, Cape Town. A large 

 quantity of mud from four different localities kindly sent to me by Dr. 

 Purcell in 1909. 



Moreover, I have received from the South African Museum, through 

 the kind intervention of Dr. Purcell, a number of alcoholic samples 

 taken from different localities in the neighbourhood of Cape Town. 



It will be seen from the above communication that a very extensive 

 material for the study of the fresh-water Eutomostraca of the Cape 

 Colony has been placed at my disposal, and I venture, therefore, to 

 believe that the present account will be rather a complete one, com- 

 prising in reality the great majority of the species which are to be 

 found in that region. 



The Cladocera of Cape Colony belong to the three following families : 

 Daphniidae, Macrothricidae and Chydoridae ; the Sididae, Bosminidae 

 and Polyphemidae not being represented. 



FAM. DAPHNIIDAE. 



GEN. 1. DAPHNIA, O. Fr. Muller. 



Remarks. In his Revision of the Cladocera Dr. J. Richard has 

 divided this genus into two groups, according to the presence or absence 



