202 Journal of Agricultural Research voi.xx,No. 3 



As shown in the preliminary experiments with various chemicals, 

 chlorinated lime up to double the amount used for sterilizing drinking 

 water does not affect snails at all. It was found, furthermore, that the 

 presence of chlorinated lime in the proportion of i to 250,000 (about 1.3 

 parts available chlorin per million) had an inhibiting effect on the action 

 of copper sulphate on snails to such an extent that some specimens did 

 not even become prostrate in the solution. The mode of interaction of 

 the copper sulphate and chlorinated lime was not investigated, but it is 

 possible either that the liberated oxygen from the chlorinated lime may 

 counteract the effect of the copper sulphate on the enzyms, or that a 

 chemical reaction takes place which precipitates the copper. If the 

 latter is true it might be feasible to remove copper sulphate from solution 

 in water by the use of chlorinated lime, in case this should for any reason 

 be desirable after using it in destroying algae, snails, or other organisms. 



A number of practical field experiments were carried out to demonstrate 

 the effectiveness of copper-sulphate treatment for snails in actual practice. 



The first experiment was conducted on a pool in the vicinity of Corval- 

 lis estimated to contain about 113,000 liters of water. This pool was a 

 portion of a stream which dries up during the summer, leaving isolated 

 bodies of water, probably connected by seepage through the sandy sub- 

 stratum. The pool contained patches of Spirogyra here and there 

 together with a number of higher aquatic plants (Veronica, Cicuta, and 

 others). The fauna included frogs, newts, and stickle-backs among 

 vertebrates, and a great variety of insect life, the most abundant forms 

 being Notonectids, Corisids, damsel fly larvae, neuropterous larvae, and 

 beetles of various kinds, both adults and larvae. Five species of mol- 

 luscs were present. Physa occidentalis and the small bivalve Musculium 

 walkeri were abundant in the aquatic vegetation. Fluminicola fusca 

 was abundant, and Goniobasis plicifera was fairly common on the sandy 

 bottom, especially around the edges of the pool, and an unidentified 

 Planorbis occurred sparingly in the vegetation. 



On August 26, 113 gm. of commercial copper sulphate were dissolved 

 in about 10 liters of water and sprinkled on the surface of the pool by 

 means of a watering pot, making approximately a 1 to 1,000,000 solution, 

 but without making any allowance for impurity of the copper sulphate, 

 absorption of algae, combination with organic matter in solution, or 

 dilution by seeping in of fresh water. 



The effect of the experiment was studied 48 hours later. The masses 

 of algae had been killed, but the higher plants, vertebrates, including 

 the stickle-backs, and the various kinds of insects were apparently 

 unharmed. No living specimens of Fluminicola or Planorbis could be 

 found, though hundreds of dead ones were seen lying on the bottom. 

 The majority of the Physae were dead, but a few seemed to be merely 

 prostrate. Some specimens of Goniobasis were withdrawn into their 

 shells and were evidently not dead. All the Musculium were lying on 



