538 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



is for the entrance of the water, and is, therefore, the front 

 end. The other end of the tuhe is closed by the filtering 

 apparatus — simply a piece of No. 20 bolting silk, or 

 coarser, if required, which is fixed in the usual manner 

 by a clamp ring. 



To one side of the tube is attached a heavy strip of 

 lead (fig. 7) to keep the instrument from being pulled 

 out of the water. This will consequently be the under 

 side, and to the opposite and upper sides of the tube, at 

 the front end of the cylindrical portion, two ring attach- 

 ments are screwed, by which the whole apparatus is 



Fig. 7.— The "Plankton-Kohre." 



fastened to the hauling rope. The action of the instru- 

 ment, when pulled at a considerable speed, depends on the 

 small area of the opening, which allows but little water 

 to enter, and therefore there is but little strain on the 

 silk tissue, so that this is not torn nor are the organisms 

 damaged. I have seen it used successfully at a speed of 

 eight and a half knots. One disadvantage is that very 

 small catches are obtained, even when towed rapidly for 

 a quarter or half an hour, but since the apparatus was not 

 intended for obtaining large quantities, this does not 

 detract from its usefulness. 



