We have attempted to adapt this system to larger plankton nets, 

 but, instead of opening and closing the mouth, we tried opening 

 and closing the cod end. This has proved difficult largely because 

 it seems to be impossible, using a fine mesh net, to get all of the 

 plankton to converge in the cod end by the times of opening and 

 closing the net. 



Finally, our mechanical devices have esentially included the 

 original design of the Clarke-Bumpus sampler greatly enlarged 

 and vastly improved with regard to opening and closing techniques. 

 Such a sampler with a MECHANICALLY CONTROLLED DAMPER 

 SYSTEM is shown in figure 18. 11. It consists of a damper closing 

 unit with a net attachment. The damper is controlled by sliding 

 nnessengers down the wire which contact the lines at the top of 

 the frame. The inside diameter is approximately 1 foot and the 

 cyclometer housing is made of 3/8-inch thick polyvinyl tubing. 

 Such a sampler has proven highly satisfactory and has an advan- 

 tage in the fact that several units may be placed on the wire and 

 tripped simultaneously. 



My purpose in hurriedly showing you as many sampling 

 apparatuses as possible has been to introduce some of the present 

 thinking with regard to instrumentation of biological samplers. 

 The instruments cited represent only a small percentage of 

 those used in oceanography and are essentially designs and 

 developments from the Woods Hole Oceanographic Institution. 

 The plankton biologist deals with a heterogeneous distribution 

 of organic particles in sea water; his needs for continuous 

 three-dimensional monitoring are great. There is no doubt 

 in nny nnind that this void will persist until proper instrumen- 

 tation engineering is applied. 



210 



