Nov. i, 1920 Control of Fluke Diseases 203 



the bottom with their shells tightly closed. Another examination was 

 made on August 30, and at this time all specimens of Physa, Flumini- 

 cola, Planorbis, and Musculium and the majority of the Goniobasis 

 were dead, but about one-third of the last had revived and were appar- 

 ently well again. This fact was evidence that practically all the copper 

 sulphate had been removed either by absorption by the algae or by 

 the dissolved organic matter, increased by the disintegration of thou- 

 sands of snails or by seepage through the sandy substratum, since it 

 had previously been fully demonstrated that Goniobasis remained pros- 

 trate even in a 1 to 5,000,000 solution of copper sulphate. 



A similar experiment was carried out on another pool of similar kind 

 and with practically the same fauna and flora; this pool was, in fact, 

 another isolated portion of the same stream. This time a copper- 

 sulphate solution of 1 to 500,000 was made. All molluscs were appar- 

 ently dead in 48 hours, and none subsequently revived. No other 

 higher animals were affected at all. 



To test the use of copper sulphate for destroying snails in a flowing 

 stream, an experiment was attempted in Oak Creek, near Corvallis, 

 Oreg. The water in this creek is cold and clear and flows rapidly. 

 The stream is very uneven as to width, depth, and speed, consisting, 

 in fact, of a series of sluggish pools connected by rapids and cascades. 

 At this season of the year, September 1, the stream was very low, and 

 was found to flow only about 550 liters per minute. The stream con- 

 tained enormous numbers of Goniobasis plicifera, the bottom in some 

 places being fairly covered with them. 



To treat this stream a 7-gallon keg fitted with a drawn-out glass 

 spigot which would feed a solution into the stream at an average rate 

 of 1.5 liters per hour was filled with a copper-sulphate solution strong 

 enough to make a 1 to 500,000 solution in the stream. This strength 

 of solution was used to make allowance for combination with organic 

 matter, precipitation in other ways, and error in estimation of the vol- 

 ume of the stream. The experiment ran smoothly for about 14 hours, 

 and at the end of this time the snails for at least a mile down the stream 

 were prostrate and apparently dead. Meanwhile, however, a rain storm 

 came up which in the following 10 hours approximately tripled the 

 volume of water in the stream. An attempt was made to strengthen 

 the solution fed into the water at a corresponding rate, and this seemed 

 to be successful. Pressure of other duties made it impossible to visit 

 the experiment again until 48 hours later. At this time it was found 

 that the spigot had been plugged by a particle of debris, though pre- 

 cautions had been taken to keep the solution as clear as possible. The 

 cessation of flow had evidently occurred shortly after the experiment 

 had last been visited, consequently the stream had been treated little 

 more than 24 hours. A few of the snails were dead, but the majority 

 had revived and were as active as ever. 



