Nov. i, 1920 Control of Fluke Diseases 199 



It was found that snails which were prostrate and would not respond to 

 stimuli, and were therefore apparently dead, would frequently revive 

 after being placed in fresh, aerated water for from 12 to 24 hours. The 

 only criterion for death which was used, therefore, was failure to revive 

 within 24 hours after being placed in fresh water. 



Experiments, using 10 snails of a species in one liter of the solution 

 at approximately 18 to 20 C, were made as follows: 



DILUTION. SPECIES TESTED. 



i to 100,000 Goniobasis plicifera, Limnaea bulimoides, Physa occidentalis . 



1 to 500,000 Fluminicolafusca, Goniobasis plicifera, Physa occidentalis . 



1 to 1,000,000 Ancylus caurinus, Fluminicolafusca, Goniobasis plicifera, Limnaea 



bulimoides, L. proxima rowelli, Physa nuttalli, P. occidentalis, 

 Planorbis callioglyptus. 



1 to 1,500,000. . .Fluminicolafusca, Goniobasis plicifera, Physa occidentalis . 



1 to 2,000,000. . .Fluminicolafusca, Goniobasis plicifera, Limnaea bulimoides, L. prox- 

 ima rowelli, Physa occidentalis, P. nutalli, Planorbis callioglyptus. 



1 to 2,500,000. . .Fluminicola fusca, Goniobasis plicifera, Limnaea bulimoides, L. prox- 

 ima rowelli, Physa occidentalis. 



1 to 3,000,000. . .Fluminicola fusca, Goniobasis plicifera, Limnaea bulimoides, Physa 

 occidentalis. 



1 to 4,000,000. . .Physa occidentalis. 



i to 5,000,000. . .Fluminico la fusca, Goniobasis plicifera, Limnaea bulimoides, L. 

 Proxima rowelli, Physa nuttalli, Physa occidentalis . 



1 to 10,000,000. .Limnaea bulimoides, Physa occidentalis. 



The results of these experiments may best be summarized as follows: 



1. All species of snails experimented with, eight in all, belonging to 

 six genera and as many families, are similar to each other in their suscepti- 

 bility to copper sulphate. There is, in fact, much more individual 

 variation shown than there is difference between species. Ancylus, 

 Fluminicola, Limnaea, and Planorbis become prostrate a little more quick- 

 ly than do Goniobasis and Physa. Goniobasis has a little more recupera- 

 tive power than the other species after being placed in pure water. 



2. All species die within 48 hours, many specimens sooner, in solutions 

 of 1 to 500,000 and 1 to 1,000,000. Fluminicola, Limnaea, Physa, and 

 Planorbis die within 48 hours in solutions of 1 to 1,500,000 and 1 to 

 2,000,000, but a few specimens of Goniobasis and one specimen of Limnaea 

 proxima rowelli revived slightly after being placed in fresh water for 24 

 hours but died within 48 hours. 



3. A 1 to 500,000 solution appeared to be no swifter in its action than 

 was a solution of 1 to 2,000,000. In all dilutions between 1 to 500,000 

 and 1 to 2,000,000 some specimens revived after exposure for 24 hours, 

 whereas after 48 hours none revived except as noted in the preceding 

 paragraph. 



4. Solutions ranging between 1 to 2,500,000 and 1 to 5,000,000 killed 

 50 per cent or more of the specimens, but not all, whereas all specimens 

 revived after 48 hours in a 1 to 10,000,000 solution, although they became 

 sick or prostrate while immersed in it. 



