350 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



others. It is seen that the shear net is fairly constant 

 throughout the three years, with a value of about 2(> to 

 37. The number for the Yngel trawl is about twice that; 

 but the hauls of the Yngel and the large Nansen have 

 been as yet too few to lead to any sure conclusions. 



Effect of the Propeller ox Nets at Stern. 



In Part II of this Report, last year, we alluded to 

 the criticism that had been made by Professor Kofoid 

 (and possibly by others since) that the eifect of the 

 steamer's propeller in mixing up water of different levels 

 might account for the differences that we sometimes 

 found between the catches of two similar surface nets 

 towed over the stern. After stating the conditions of the 

 case last year, we continued : " these are all points that 

 ought to be cleared up by experiment, and we propose to 

 deal with them in the coming season, and to compare, for 

 example, the catches in nets towed some little way off 

 the side of the ship with similar nets towed behind." 



During the past year we have carried out this 

 intention; and we have now a long series of observations 

 made under similar conditions at two different times of 

 year, April and August. We attached one of the two 

 exactly similar surface nets to an otter-board which was 

 towed from a position forward of the foremast on the 

 starboard side, so as to carry it out about 20 feet from the 

 side of the boat amidships. The other net was in the 

 usual position over the stern. If there were any force in 

 the criticism, the " otter-net," which was certainlj' 

 sampling surface water quite undisturbed by the pro- 

 peller, or any other part of the ship, ought to give results 

 differing from those obtained from the net at the stern in 

 water which might be supposed to be affected by the 

 action of the propeller; but no such difference is to be 

 seen. In 44 hauls of each net, taken in April, '09, the 



