242 THE AMERICAN MONTHLY [Aug. 



when we can transport ourselves to the open space of the 

 lake and on account of the reed-hoops it may only 

 be used for working at the surface of the water. The 

 material collected is subject to the same treatment, the 

 bottom glass being applied, removed and emptied — as in 

 the case of rod-net described in the second figure. Its 

 use is therefore not so advantageous and multifarious, as 

 that of the simple bag-like drag net. 



In its principles of construction the net used at the 

 Biological Station of Plon, called the plancton net is the 

 same, but there is not at its bottom any closed vessel. 

 It is provided with a tap, so that its contents may be 

 emptied into the bowl by turning the tap. 



For collecting organisms living at the bottom of lakes 

 and bringing up mud, I devised a bottom-net of which 



1 give a design in fig. 5. The outer cylinder (a) is made 

 of pretty narrow brass wire tissue. The bottom is either 

 convex or flat. The brim is formed by a brass hoop of 



2 cm. breadth, provided with rings for fastening the line. 

 Besides there are three movable clasps on it. 



The middle cylinder (b) is a bag of very narrow silk- 

 cloth, sewn to a strong brass-hoop about 2 cm. in breadth. 

 The bottom is of bag-like shape. There are three ten- 

 dons standing out from the hoop, to prevent the net from 

 sinking to the bottom or from sticking to the outer wire 

 cylinder. 



The inner cylinder (c) is made of wide meshed brass 

 wire cloth. The bottom is closed like a bag. The brim 

 is covered by a flat brass circle 2.5 cm. broad, and its 

 outer circumference is a little larger than the inner one 

 of the outer cylinder. There are three little screws 

 placed at an equal distance one from the other, provided 

 with eyes ; when using the net, the clasps are hooked in 

 the screws and the eyes then screwed down. The sepa- 

 rating and uniting of the three nets is thus rendered 

 possible. 



