22 Pmceedings of the Royal Iriah Academi/. 



rivers is, however, l)iit little known. The phytoplankton of Lough Neagh has 

 been examined by the Messrs. West ; but the catches were made only during a 

 very short season of the year. Asa matter of fact, we now know that a visit 

 to a lake like Lough Neagh would only permit us to describe the planktonic 

 flora or fauna at the particular time of the visit. The change of the seasons is 

 just as clearly marked by the changes in the plankton, that is the appearance 

 and disappearance of characteristic organisms, as by the opening of the buds in 

 spring or the fall of leaf in autumn. Up to the present time extremely little 

 has been known of the periodicity of the British fresh-water plankton. 



The relation of the lakes of Scotland to those of Europe was referred to 

 in the course of Sir John Murray's investigation of the Scottish lochs. This 

 year a paper appeared by the Messrs. West, which may be said to be the first 

 detailed paper on the subject of periodicity. It deals with the phytoplankton 

 alone, however, and that only of certain laljes in Scotland and the English Lake 

 District. It is furthermore only a qualitative research. The j)resent paper 

 is the first quantitative research on the plankton (phyto and zoo-plankton) of 

 the British lakes. 



Tlie research was commenced by one of us whilst on the staff of the 

 University of Belfast, and was enabled by the aid of grants from the Royal 

 Society and the Koyal Irish Academy. To both these bodies our thanks are 

 due. Expeditions were made to the lake at first twice in three weeks ; but as 

 time went on and one of the authors' came to Liverpool, the length of the 

 periods had to be increased. With the exception of two visits to the lake, all 

 the catches were made by one of the authors, and thus we were assured of the 

 uniformity of procedure, &c. 



A discussion concerning the use of quantitative methods is given in the 

 text. It may be said here, however, that wlrilst we consider certain features 

 of tire Eliel methods of absolute importance, we do not consider the detailed 

 practice of the Kiel School to be the only practicable way of carrying out 

 plankton research, nor is it always possible. Furthermore, we do not consider 

 the Messrs. West justified in asserting that " the more detailed work concern- 

 ing the phytoplankton, which, so far as we can see, in the British Lake areas 

 will be quite of subordinate value, can be done piecemeal at any time by 

 sufSciently qualified persons who possess the necessary means and time."- 

 At the very most the above might apply to lakes they had investigated. 



We are very much indebted to Professor Gwynne Vaughan, of Belfast 

 University, for his great kindness, which alone enabled visits from Liverpool 

 to Lough Neagh being made once every three weeks for a period. We wish 



, 1 Dakin. 



* W. West and Professor G. S. West : " Periodicity of t)ie Phytoplankton of some British Lakes." 

 Journ. Linn. Soc. Bot. xl. 1912. 



