Manchester Memoirs, Vol. Iviii. (19 14), No. 8. 3 



Early Palaeozoic rocks, while Lough Neagh is underlaid 

 by Tertiary rocks, basalt of the Miocene period. The bed 

 rocks of Rostherne Mere belong to the Triassic series of 

 the Mesozoic or Secondary period. Here again, therefore, 

 Rostherne presents an interesting comparison with the 

 other lakes. We cannot yet say whether the mode of 

 formation and the character of the underlying rocks have 

 any direct relation to the fauna and flora ; but the differ- 

 ences in these two features did seem to us to present 

 points of interest, attention to which might yield important 

 results in instituting a comparison with the fauna and 

 flora of the other lakes of Britain. We may, perhaps, 

 here point out that the character of the underlying rocks 

 of the drainage area of a lake does seem to have a direct 

 bearing on the nature of its plankton. Messrs. W. and 

 G. S- West have pointed out that, in lakes situated on or 

 draining the Pre-Cambrian and Early Palaeozoic rocks, 

 Desmids are the dominating constituent of the plankton 

 and that the rich Desmid areas correspond geographically 

 with the distribution of lakes on these primary rocks. 



Our investigations were started with the sole object of 

 studying the plankton, but we have been led to extend 

 our observations to the whole of the fauna and flora 

 in the hope of arriving at a knowledge of the inter- 

 dependence and economy of the various living organisms 

 which occur within a specified and naturally restricted 

 area and of the correlation between the planktonic and 

 benthonic forms. Completed in this way, our results will 

 we hope form a basis for comparison with the fauna and 

 flora of other British lakes. Mr. R. S. Adamson has 

 kindly undertaken an ecological investigation of the flora 

 of the mere and its surroundings, and wc hope to present 

 to the Society from time to time a series of reports by 

 specialists on the various groups of the fauna. Finally, 



