1897] MICROSCOPICAL JOURNAL 243 



Each cylinder of tliis ai)paratus has another function. 

 The outer wire cylinder is a protecting case, preventing 

 any damage to the net and ought therefore to consist of 

 pretty line cloth so as to resist branches of trees, and 

 things covering the buttoin of lakes. The middle cylin- 

 der of gauze is the real collecting net, which retains 

 organisms or slime after staining the water. The inner 

 cylinder is intended for keeping off larger objects which 

 would be liable to injure the fine silk gauze. It affords 

 only protection to the inside and consists therefore of 

 pretty wide meshes, giving easy access to water and 

 organisms. 



When working with it, we unite the different cylin- 

 ders. After this the apparatus is lowered into the lake 

 by the pulling line fastened to the rings. Then slowly 

 advancing the boat, we tow it a certain time, until it 

 naturally fills with organisms and slime. Having drawn 

 out the apparatus, we separate the cylinders, by loosen- 

 ing the screws and take out the gauze cylinder with the 

 matter contained in it. The conservation is then carried 

 out in the same way as formerly described, but if there 

 be too much mud in the net, its greater part is removed 

 by dipping the net several times into the water. 



For investigating certain fauna I have devised another 

 dredge, shown in fig. 6., consisting of two parts, the 

 shutting cover and the net proper. 



The shutting apparatus (a) is formed by a brass frame 

 standing somewhat obliquely, with a wide semicircular 

 mouth. It is closed by a trap door also of brass, which 

 may be raised or lowered. There is a small ring in the 

 middle of this trap door near its horizontal edge, to 

 which a line is tied. On both sides of this suspension 

 ring there are two brass sticks with knobs on their ends; 

 these are fastened to the frame but are ni()val)le, so that 

 they are raised when the trap is oi>oued and lowered 

 when the trap is closed, sliding in the holes which are 



