514 



PLANKTON OF THE SYDNEY WATER-SUPPLY, 



lema eriensis in either swamp or creek or pond, save that I 

 found a single frustule in the pond at Pott's Hill, which, 

 however, has been formed entirely by a scour from the filter- 

 screens. 



It was abundantly evident, from the general character of 

 the plankton, that the water of the Supply is mainly derived 

 from the storm-water brought down by a multitude of creeks 

 to the river, and not from the drainage of swamps. The 

 microscopic flora is just such as I have often squeezed out of 

 the heads of tufty weeds in creek-pools. Further evidence 

 to the same end is afforded by the gratifying absence of 

 Anabfena, of which I cannot I'emember to have noted a single 

 filament, and of Trachcloinoiidf! among the Infusoria, two 

 organisms, which, T think, may be considered as characteristic 

 of swamp-life in this country. Indeed, with the exception of 

 Oscillatoria nigroviridis var. rrassn, and Scytonema mirabile, 

 the Myxophyceat: are conspicuous by their absence. 



The following synopsis will serve to show the general bal- 

 ance of parts in the flora and fauna of the plankton. The 

 numbers indicate species and well marked variations ; this 

 makes the Desmids appear more numerous than they really 

 are. 



Flora. 

 Chlorophycese generally 

 Desmidiaceae 

 Myxophycese 

 Bacillariacese 

 Phythelieje 



Fauna. 



60 

 112 

 19 

 48 

 16 



Peridinieje 



Infusoria ... 



Rotatoria . . . 



Rhizopoda 



Vermes 



Entomostraca 

 This table, however, gives quite a fictitious idea of 

 appearance of the material from the filter-screens, 

 majority of organisms included are quite rare, having been 

 noted to the extent of anything between one specimen only, 

 and one specimen to each drop examined . Considering the 

 richness of the slimes, the accumulated screenings of 48 

 hours, this means that they do not bulk very largely in the 



13 



35 



14 



13 



3 



3 



the 



The 



