SECTIONAL TRANSACTIONS.—D. 387 
the plankton indicator, used on herring drifters during 1930-1934. Positive 
correlations between the number of herring caught and their food Calanus 
and negative correlations with phytoplankton have been demonstrated. 
Other correlations are suggested. The instrument is now used com- 
mercially. The progress made with a wide survey of the plankton by 
means of continuous plankton recorders towed by steamships crossing the 
North Sea is briefly described, and a general review made of the distribution 
of the herring fisheries in relation to the plankton. The continuous re- 
corder survey is being conducted in close association with the Fisheries 
Department of the Ministry of Agriculture and Fisheries, who are making 
a more detailed study of the plankton in relation to the herring in certain 
areas of the North Sea. 
Mr. R. S. Wimpeenny.—The plankton communities of the North Sea 
and their relation to the herring fishery. (A résumé of work done 
by Lowestoft Planktologists) (12.30). 
It has already been shown that the phytoplankton forms at times such 
dense patches that the movements and shoaling of the herring are inter- 
fered with. In this contribution the development and movements of these 
patches are considered for the past twelve years, but with especial reference 
to 1933 and 1934. 
1933 produced the most luxuriant and dense growth of Rhizosolenia 
styliformis yet observed and also an unusually high salinity in the area of 
its occurrence. This was difficult to account for, and the possibility of 
its having been caused by the photosynthetic activity of the diatom itself 
is discussed. 
In both 1933 and 1934 there was a tendency for the autumn herring 
shoals (as revealed by the charted catches) to mass against the edge of a 
diatom patch. A similar orientation was observed when some of the 
zooplankton organisms caught by the Hensen net were charted. Zoo- 
plankton are not absent even in dense phytoplankton patches, but in these 
areas the community consists of a greater proportion of young forms. It is 
possible that the phytoplankton patches may be nursery grounds and there 
may be a physiological gradient for the zooplankton between the edge and 
centre of a patch. Similarly herring that shoal prior to spawning may 
be taking up a position in relation to the phytoplankton patch that has a 
connection with the physiology of reproduction. 
AFTERNOON. 
CENTENARY OF THE LANDING OF DARWIN ON THE GALAPAGOS ISLANDS, 
AND OF THE BIRTH OF THE HYPOTHESIS OF THE ‘ ORIGIN OF SPECIES.’ 
Prof. Sir E. B. Poutton, F.R.S.—Introduction (2.15). 
Prof. J. H. AsHwortu, F.R.S.—Charles Darwin in Edinburgh, October 
1825 to April 1827 (2.45). 
Information obtained chiefly from a notebook of observations made by 
Darwin and from the minute book of the Plinian Society of the University 
of Edinburgh, a biological society of which Darwin was a member from 
November 28, 1826, until he left Edinburgh in April 1827. 
