METHODS OF PLANKTON RESEARCH. 



505 



weight, is not allowed to hang on the silk net, but is 

 supported separately by three cords, which are fastened to 

 the stout lower ring of the conical mouth-piece. 



The size of the net and the method of cutting it can 

 be seen from fig. 2, where the right-hand sketch is a 

 representation of the net when sewn up, and the other 

 figure is the same unrolled, showing the pattern as it 

 should be cut out. For the middle plankton net the 

 radius r of the mouth of the net is 20 cm. The radius r 



Fig. 2.— B = 20 cm. ; r = 3 cm. ; x = 17-65 cm. ; y = 100 cm. ; and 

 the angle a = 61-2°. 



of the bottom of the net, where it is attached to the metal 

 bucket, is 3 cm. The portion of the cone is cut oft' (fig. 2, x.) 

 is 17'65 cm., and the length of side remaining 100 cm. 

 Care must be taken to allow of a margin when cutting 

 out the pattern, so that the edges AC and BD can overlap 

 and be sewn together, the upper edge of the net be sewn 

 to the linen strip, and the bottom of the net fixed by the 

 clamp ring to the bucket. 



The metal bucket serves as a receiver for the 

 plankton and furthermore does away with the use 

 of the filtrator invented for use with the great Hensen 



