MARINE BIOLOGICAL STATION AT PORT ERIN. 305 



There is a tendency, in trying to attain to more exact 

 methods in biology, towards arguing and collecting, as if 

 organisms were evenly distributed through the particular 

 layer of water or region they inhabit — as if, in fact, they 

 were like the salts dissolved in the water, so that one sample 

 from a locality ought to be exactly like any other sample. 

 This is far from being the case. One gallon or cubic foot 

 of water, though, in the main, like its neighbours, may con- 

 tain one of the rarer organisms not present in the next gallon 

 examined. Consequently, in a net hauled up vertically, 

 or in a comparatively small volume of water drawn up from 

 a special layer through the hose-pipe, there is considerable 

 risk of missing some of the less frequent organisms ; 

 while the ordinary tow-net, through which a very much 

 greater mass of water passes, will probably contain a more 

 completely representative gathering. This is, in the 

 main, our objection to the pump-plankton method which 

 we tried at Port Erin at Easter on board the fisheries 

 steamer " John Fell." Equal times of working with the 

 ordinary open tow-net and with the pump and hose gave 

 results, both at bottom and at surface, which were 

 absurdly disproportionate. The open tow-net collected in 

 the same period many times as much material, and far 

 more species than the pump showed. 



Mr. Thompson, in his note on a previous page as to 

 Copepoda, has referred to the interesting differences we 

 found between surface and bottom (30 fathoms) plankton 

 in mid- winter. We hope to continue such observations in 

 the deeper water lying between the Isle of Man and Ire- 

 land. That, however, can only be done on our 

 comparatively rare steamboat expeditions. In the mean- 

 time our Curator at the Station has endeavoured, during 

 the whole of the past year, to take at least one ordinary 

 surface tow-net gathering across Port Erin 13ay in the 



