Direction of Tow 



Propeller shaft, 



Plankton 



trapped between two silk bands 

 and stored in tank of formalin. 



Fig. 6. The 'Hardy' Continuous Plankton Recorder, used to sample plankton along the routes 

 of commercial and other ships on passage. The upper figure depicts the recorder being towed 

 by a cargo vessel, and below it is a diagram showing the internal mechanism of the instrument. 

 The chart shows the lines of regular monthly sampling as at i January 1961 organized by the 

 Edinburgh Oceanographic Laboratory of the Scottish Marine Biological Association. The open 

 circles show the positions of the Weather Ships. 



