SEA-FISHERIES LABORATORY. 139 



to investigate, one would expect that there would be more 

 variety in the plankton than if only one or two samples 

 had been taken in the period. This is the case. In 

 September no less than fifty-eight different kinds of 

 organisms fall to be recorded. Professor Herdman, in 

 his work on the " Madge," used five different kinds of nets, 

 all made of fine silk bolting cloth, as follows : — 



A Hensen-Petersen closing net, with 200 meshes to 

 the inch. 



A small Apstein net, with 212 meshes to the inch. 



An ordinary tow-net, weighted to work below the 

 surface, 120 meshes to the inch. 



An ordinary surface net, 120 meshes to the inch, used 

 for the first time. 



An ordinary surface net, 120 meshes to the inch, that 

 had been in use for a year. 



The five nets were not often used simultaneously, as 

 a rule only the surface and deep-water nets were worked 

 at the same time. On measuring and examining the 

 material collected, it was found that, although the 

 gatherings were taken in equal periods of time in a very 

 limited sea area, there was no strict uniformity, either in 

 quantity or kind of organisms captured. Sometimes the 

 surface net contained more material than the deep one, at 

 other times there was more in the deep net than in the 

 surface one. The old surface net appeared to fish better 

 than the new one. The Apstein net invariably had a 

 smaller catch than the ordinary net. When we find such 

 differences in a small section of the Irish Sea, , what 

 must be the conditions when the whole area is fully 

 investigated ? 



It is proposed, in this Report, to deal with the 

 distribution of organisms, and to show that differences in 

 the nature of the plankton are more frequently than 



