20 PBOCEEDIJTGS OF THE 



I have published elsewhere* during the last year some obser- 

 vations that confirm me in the belief that the plankton in the 

 ocean, which is directly or indirectly the food of fishes, has no 

 such uniformity of distribution as is sometimes supposed. If, 

 then, this uniformity does not exist over wide areas, how can we 

 pretend to investigate such an enormous region as the North Sea 

 by means of comparatively few and distant observations ? We 

 must, in my opinion, learn the meaning and value of our work by 

 the intensive study of areas such as the Firth of Forth, Kiel Bay, 

 Plymouth Sound, or Liverpool Bay, before attempting the English 

 Channel, the Irish Sea, or the Clyde Sea-area, and these again 

 before tackling the relatively enormous North Sea, which is at 

 least twenty times the size of the Irish Sea. 



Convinced of the fundamental importance of such work, I spent 

 the greater part of the last summer vacation in experimenting 

 day after day with various plankton nets under similar and under 

 varying conditions in a limited sea-area oif Port Erin in the Isle 

 of Man — with results that were startling in their diversity. It 

 was obvious that the plankton Avas at that time very unequally 

 distributed over the depths, the localities, and the dates. It 

 seemed clear that one net might encounter a swarm of some 

 organism which a neighbouring net escaped, and that a sample 

 taken on one day might be very different in quantity from a sample 

 taken imder the same conditions next day. 



I stopped this series of observations on September 17th. After 

 a few days of Avind a spell of quiet, calm weather followed, during 

 which I took some tow-nettings both inside Port Erin Bay and 

 outside, both in the day and at night, and all of these differed 

 entirely in character from the gatherings of the previous weeks — 

 being composed mainly of Chcntoceros and other Diatoms. During 

 this period of calms and Ught easterly winds the surface of the 

 sea was smooth and the water was distinctly coloured by the 

 abundance of Diatoms. When the weather broke again, at the 

 end of September, another abrupt change took place, and gatherings 

 taken at the beginning of October showed very few Diatoms but 

 many Copepoda. It is evident that if any observer had been 

 taking quarterly or even monthly samples of the plankton in that 

 sea-area, he w-ould have obtained very different results, according 

 to the exact date of his visit. On three successive weeks about 

 the end of September he might have found evidence for as many 

 different far-reaching views as to the composition of the plankton 

 in that part of the Irish Sea. How it can be supposed that hauls 

 taken miles apart and repeated only at intervals of months, or 

 even weeks, can give any sure foundation for calculations as to 

 the population of wdde sea areas, I fail to see. 



These conclusions need not lead us to be discouraged as to the 

 ultimate success of scientific methods in solving what may be 

 called world-wide problems, but they suggest that it might be 



* Trans. Biol. Soc. Liverpool, vol. xxi. p. 1. 



