SEA-FISHERIES LABORATORY. 105 



MONTHLY INVESTIGATION OF THE PLANKTON 

 BY THE HENSEN NET METHOD. 



By Andrew Scott. 



This investigation was commenced in January, 1907, 

 with the intention that regular hauls should be taken at 

 intervals of one month, between Piel Gas Buoy, at 

 the outside entrance to the Barrow Channel, and Great 

 Ormes Head, on the North Wales coast. Owing to 

 unforeseen circumstances the continuity of the observa- 

 tions was interrupted on three occasions : no hauls were 

 taken in April, July and December. In the absence of a 

 complete series of monthly observations it would be 

 unwise in the present report to discuss the changes that 

 take place, from month to month, in the pelagic 

 organisms along the line of observation. At the same 

 time, one or two interesting facts can be detected by a 

 review of the tables of results given below, which are 

 worth some attention. 



Three stations have been laid down along an 

 imaginary straight line, joining Piel Gas Buoy to Great 

 Ormes Head. The first station is four and a half miles, 

 the second twenty-two and a half, and the third forty and 

 a half miles from Piel Gas Buoy. The third station is 

 four and a half miles off the Orme's Head, and the middle 

 station is eighteen miles equidistant from the first and 

 third. At each station the ship is stopped, and when all 

 way is off her the net is put over the side, lowered down 

 to a depth of ten fathoms and then slowly drawn to the 

 surface. The time taken to draw the net up through ten 



