386 SECTIONAL TRANSACTIONS.—D. 
of muscular contraction and other mechanisms where the immediate process 
is an anzrobic one. 
Mr. L. C. BeapLe.—Osmotic regulation in some brackish water inverte- 
brates (10.30). 
Experiments with several brackish water animals (Gunda ulve, Nereis 
diversicolor, Nereis virens and Arenicola marina) have shown that the weight 
changes undergone on transference from normal to dilute sea-water are 
essentially similar in all these forms. A rapid rise in weight due to uptake 
of water is checked at a maximum considerably lower than would be expected 
if osmotic equilibrium were established. There follows a fall to an 
equilibrium value above the original weight. The general activity may 
fall during this process, but is ultimately regained. A typical marine 
invertebrate such as Nereis cultrifera, when subjected to these conditions, 
will take up water continuously until osmotic equilibrium is reached. The 
nature of the water control in the above brackish water forms is under 
investigation. Experiments indicate (1) that different species and in- 
dividuals of the same species at different seasons differ in their powers of 
control ; (2) that the water enters the body through the skin; (3) that the 
rate of entrance and consequently the power of control is influenced by 
temperature and by the calcium content of the sea-water ; (4) that the water 
content of the body is not primarily controlled by the excretory organs, 
but that the animal is able to regulate the rate of inflow through the skin. 
Symposium on The herring problem (11.0) :— 
Mr. E. Forp.—The nature, exteyt and significance of vertebral vari- 
ation in the herring with reference to the ‘ race’ problem (11.0). 
Dr. W. C. Hopcson.—Recent additions to the knowledge of the 
herrings of the southern North Sea (11.30). 
Since it became possible to forecast the general characteristics of the 
main fishery of the southern North Sea, attention has been directed to the 
study of factors which have an influence on the swimming of the herrings. 
Besides phytoplankton concentrations, it appears that wind, either before 
or during the fishery, has a considerable effect on the catches of the drifters, 
and a detailed study of the variation in the amount of fish landed in relation 
to the direction of the wind is at present being carried out. 
Further, lunar influence on the catches of herrings, especially in the 
southern part of the North Sea, is considerable, and the characteristics of 
the fishery vary according to the date of the October full moon. 
It is also evident that there is a connection between the relative strength 
of year-classes and the temperature of the water in January in the Channel, 
which is the main spawning ground of the herrings of the southern area. 
Prof. A. C. Harpy.—The herring in relation to the plankton (12.0). 
Earlier work on the planktonic food of the herring is reviewed and 
reference made to the work of Pearcey, Savage and Hardy on the influence 
of phytoplankton on the herring. Recent work carried out with Dr. G. 
T. D. Henderson, Mr. C. E. Lucas and Mr. J. H. Fraser from the Uni- 
versity College of Hull is described. ‘The distribution of the herring in 
relation to that of the plankton is studied by experiments with an instrument, 
