300 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



THE PLANKTON ON THE WEST COAST OF 

 SCOTLAND IN EELATION TO THAT OF 

 THE IEISH SEA.— Part IV. 



By W. A. Herdman, F.E.S., and Wm. Eiddell, M.A. 



We have now completed seven years (1907-1913 

 inclusive) observations on the summer plankton in the 

 seas to the West of Scotland ; and, as the British Associa- 

 tion meeting in Australia in 1914 renders it impracticable 

 to carry on work from the " Euna" in the coming summer, 

 this seems a fitting opportunity to close this series of 

 observations, and draw such conclusions as we can. 



In our first Part* we dealt with the work carried on 

 during the first four summers (1907-1910 inclusive), and 

 showed : — 



1. That a considerable difference existed between 



the summer plankton in Hebridean Seas and 

 that of the Irish Sea at the, same time. 



2. That the phyto-plankton, which had disappeared 



from the Irish Sea by July, was still present in 

 some parts of the Hebrides. 



3. That some localities, in the Hebrides, not far 



apart, differ very considerably in the nature of 

 their plankton at the same time of year. 



4. That there is a constancy year after year in the 



nature of the plankton at some localities at corres- 

 ponding times. 

 In that report we gave evidence to show that " off the 

 north-west coast of Scotland, at one time of year (July) 

 in several successive seasons, the plankton, as sampled by 

 vertical hauls, was of different types (zoo- or phyto- 



* This Report for 1910, p. 60. 



