INVESTIGATION OF THE PLANKTON OF THE IRISH SEA. 141 
SPOLIA RUNIANA.—V, Summary of Results of Continuous Investigation of 
the Plankton of the Irish Sea during Fifteen Years. By Sir WILLIAM 
A. HERDMAN, C.B.E., F.R.S., F.L.S., Emeritus-Professor of Natural 
History in the University of Liverpool. 
(PLATE 7 and 2 Text-figures.) 
[Read 2nd March, 1922.) 
INTRODUCTION. 
Tue history of this investigation, which has now extended over fifteen years 
(1907-21 inclusive), is briefly as follows :—After collecting and examining 
samples of marine plankton in a casual and sporadic manner for over quarter 
of a century on various parts of the British coast, in the winter of 1905 
I hecame impressed with the view that the only hope of solving some of the 
problems of the plankton lay in a much more exhaustive study of a much 
greater number of samples taken as frequently as possible throughout the 
year at one locality, or series of localities, and extending over several years *. 
My connection with the Port Erin Biological Station and the staff at work 
there and in the Zoological Department of the University of Liverpool 
afforded the opportunity of organising a scheme of co-operative research, 
which later on became crystallised into six “ official” hauls of the plankton 
net per week throughout the year, and a much greater number of * special ” 
hauls (often ten or a dozen per day at sea, and amounting to as many as 36 
hauls, in a small area two miles in extent, on one occasion) during certain 
critical months of the year (March, April, July, August, and September) 
when the plankton was speciaily abundant or was rapidly changing in 
character. The “official” gatherings were taken by the staff of the Bio- 
logical Station inside Port Erin bay and consisted on each occasion of two 
horizontal surface-hauls across the middle of the bay, about half a mile, and 
one vertical haul, from 6 fathoms, close to the buoy at the entrance. The 
“special” hauls were taken by myself from a steamer both inside Port Erin 
bay and also at fixed “stations”? in the open sea at distances of 3, 5, and 10 
miles from land, with occasional days in the deep water (60 to 70 fathoms) 
halfway from the Isle of Man to Ireland, 
For these purposes, during the summer of 1406, I chartered the steam- 
launch ‘ Madge,’ and used her for a preliminary survey of the ground and 
* The research has, however, extended over a much longer period than was at first con- 
templated, but new developments in the work kept opening up, and the value of cumulative 
evidence was impressed upon me, It was felt necessary to have thousands of samples to 
deal with and a number of years to compare. 
LINN, JOURN.— BOTANY, VOL. XLVI. M 
