MARINE BIOLOGICAL STATION AT PORT ERIN. 31 



water obtained by means of closing water-bottles from 

 various zones in the ocean. Rut even if deficiencies in 

 the nets be thus made good by supplementary methods, 

 and be allowed for in the calculations, there still remains 

 the second and more fundamental source of error, namely, 

 unequal distribution of the organisms in the water; and 

 in regard to this a large amount of evidence has now been 

 accumulated, since the time when Darwin, during the 

 voyage of the " Beagle " on March 18, 1832, noticed off 

 the coast of South America vast tracts of water discoloured 

 by the minute floating Alga 3 Trichodesmium erythrceum, 

 which is said to have given its name to the Red Sea, and 

 which Captain Cook's sailors in the previous century 

 called " sea-sawdust.'' Many other naturalists since have 

 seen the same phenomenon, caused both by this and by 

 oilier organisms. It must be of common occurrence, and 

 is widespread in the oceans, and it will be admitted that 

 a quantitative net hauled vertically through such a 

 Trichodesmium bank would give entirely different results 

 from a haul taken, it might be, only a mile or two away, 

 in water under, as far as can be determined, the same 

 physical conditions, but free from Trichodesmium. 



Nine nations bordering the North-West seas of 

 Europe, some seven or eight years ago, engaged in a joint 

 scheme of biological and hydrographical investigation, 

 mainly in the North Sea, whh the declared object of 

 throwing light upon fundamental tacts bearing on the 

 economic problems of the fisheries. One important part 

 ol their programme was to test the quantity, distribution. 



and variation of the Plankton by means of periodic 



observations undertaken lour 1 imes in the year i February, 

 May, August and November) at certain fixed points in the 

 sea. Many biologists considered that these periods were 

 ton trw and the chosen stations too Ear apart to give 



