CH. Vl] QUANTITATIVE PLANKTON INVESTIGATIONS 



125 



This is represented in Fig. 25 and consists of a metal funnel 

 which terminates in a cyhnder which is made of the same silk 

 which is used for the net fabric. The lower end of this cylinder 



Fig. 25. The Hensen " Filtrator." 



is a ground brass ring which is tightly screwed down to a glass 

 plate from which it can be detached. The contents of the bucket 

 are run into the funnel and the water passes through the silk side 

 of the cylinder ^vhile the catch remains on the glass plate. After 

 the net has been discharged it is washed on the outside with a 

 stream of water from the hose so as to wash down into the bucket 

 any organisms w^hich are attached to the interior walls of the 

 apparatus, and the bucket is again emptied into the filtrator. The 

 frame of the filtrator is then unscrewed and the catch is removed 

 from the glass plate, bottled and labelled^. 



1 On board the John Fell the use of the filtrator has been dispensed with 

 without detriment. When the net is hauled the contents of the bucket are simply 

 run out into a little silk net about three inches in diameter and about six inches 

 long. To the inside of this net a silk thread is attached so that it can con- 

 veniently be turned outside in. The catch remains at the apex of this little net. 



