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in. 



THE PLANKTON OF LOUGH NEAGH : A STUDY OF THE SEASONAL 

 CHANGES IN THE PLANKTON BY QUANTITATIVE METHODS 



By W. J. DAKIN, D. Sc, F.L.S., 



Senior Assistant in the Department of Zoology and Comparative Anatomy 

 University College, London ; 



AND 



MARGARET LATARCHE, M. Sc, Zoology Department, Liverpool University. 



Plates IV- VI. 



(being the eleventh report from the fauna and flora committee.) 



Read November 11, 1912. Published Januabt 27, 1913. ' ' 



Preface. 



Twenty-two years ago Hensen, the veteran physiologist of Kiel, founded the 

 Kiel School of Quantitative Plankton Research. Whatever may have been 

 said in criticism of Hensen's work, there is no doubt that he provided a new 

 stimulus which set plankton investigations on a different basis and aroused 

 fresh enthusiasm in this line of research. 



Whether the investigations have been carried out quantitatively or 

 qualitatively, they have, since the detailed work of Hensen and his colleagues, 

 been placed on a systematic foundation. Attempts have been made to 

 determine the periodicity of the plankton, that is to say, the changes taking 

 place throughout the year. In the succession of years it has been found that 

 these changes take place in a regular and, on the whole, similar manner. Yet 

 different years are perhaps marked by small variations in the time at which 

 the different organisms attain their maximum development. Again, different 

 lakes (varying in latitude, altitude, or environment) present interesting 

 deviations, some large and some small, which have led to the study of the 

 correlation of changes in the plankton with environment and meteorological 

 phenomena. 



The interest in the fresh-water plankton has advanced perhaps more 

 rapidly than the interest in the marine plankton. This is probably due to the 

 ease with which problems could be investigated in fresh-water owing to the 

 foundation of biological stations. This applies particularly to the Continent, 



