3812 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
COMPARISON OF NETS. 
One of the objects of this investigation was to 
compare the performances of the different nets, and try to 
determine, if possible, which nets could be relied upon to 
give most nearly representative samples of the plankton. 
CoARSE AND FINE SuRFACE NETS. 
The influence of the mesh of the net upon the volume 
and nature of the catch is well known to all who have 
had much experience in collecting plankton, and it was 
remarked upon in last year’s report. With the object of 
getting more definite information on the matter, and also 
because we were convinced from daily observation that 
our fine (No. 20) nets were not giving us adequate 
samples, after occasional trials we started, in September, 
1908, using a “coarse’’ surface net (No. 6 silk) on all 
occasions along with a fine net of exactly the same size 
and shape. ‘The results are very interesting |§ When 
there is much macro-plankton in the water the coarse net 
catches much more than the fine, as is shown in the 
following examples taken at a time of year when 
Copepoda and other larger Crustacea are abundant on the 
surface :— 
Sept. 16. Sept. 17. Oct. 8. Oct. 12. Oct. 14. 
Coarse net 19°0 10:0 9:7 14°5 10°5 
Fine net 0°6 0°5 1°8 1:0 0°75 
But, on the other hand, when the bulk of the plankton is 
very minute (such as Diatoms and Dinoflagellates), the 
fine net may catch most, as in the case of the following 
examples : — 
April 23: coarse net 3 c.c.; fine net 17 c.c. 
April 29: coarse net 6°5 c.c.; fine net 11 c.c. 
