66 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



6,000 hauls have been taken, carefully analysed, and the results 

 fully discussed in a series of special reports on this " Intensive 

 Study of the Plankton " which have been laid before and 

 published by the Lancashire Sea-Fisheries Committee. 



The following instance gives an example of local distribu- 

 tion of an organism in swarms, and of the erroneous conclusions 

 that might be drawn from imperfect or incomplete observations : 



" We were fortunate enough on one occasion to obtain 

 incontrovertible evidence of the sharply defined nature of a 

 shoal of organisms, forming an instructive example of how 

 nets hauled under similar circumstances a short distance apart 

 may give very different results. On the evening of April 1st 

 (1907), at the 'alongshore' Station III., north of Port Erin, 

 off the ' Cronk ' one mile out, I took six simultaneous gatherings 

 in both surface and deeper waters. Two of the nets were the 

 exactly similar surface tow-nets which I have called B and C. 

 At half-time, as the result of a sudden thought I hauled in B, 

 emptied the contents into a jar, and promptly put the net out 

 again. This half gathering was of very ordinary character, 

 containing a few Copepoda, some Diatoms and some larvae, 

 but no Crab Zoeas. At the end of the 15 minutes, when all the 

 nets were hauled on board, all the gatherings, including B, 

 showed an extraordinary number of Crab Zoeas rendering the 

 ends of the nets quite dark in colour. B was practically the 

 same as C although B had only been fishing for seven minutes. 

 It was evident that at about half-time the nets had encountered 

 a remarkable swarm of organisms which had multiplied several 

 times the bulk of the catch and had introduced a new animal 

 in enormous numbers. Had it not been for the chance observa- 

 tion of the contents of B at half-time, it would naturally have 

 been supposed that, as all the nets agreed in their evidence, 

 the catches were fair samples of what the water contained 

 over at least the area traversed — whereas we now know that 

 the Zoeas were confined to at most the latter half of the traverse 



