forms of the asiatic clam c fluminea tcmtb was tested as a 30 solution of the active ingredient in suitable solvents for static tests of toxicity of tcmtb to juvenile c fluminea gravid adults were collected from the clear fork of the trinity river near arlington tex and returned immediately to the laboratory on return selected adults were placed in one liter of dechlorinated tap water in glass culture dishes and held overnight in an incubator adjusted to field water temperature the following morning adults were removed from the culture dishes and all spawned viable juvenile clams shell length approximately 2 mm were collected individually and transferred to glass petri dishes containing 20 ml of dechlorinated city of arlington tap water twenty five juveniles were placed in each of three replicate dishes for each concentration of the product tested three control dishes containing twenty five juveniles and no molluscicide were also set up for test purposes tcmtb was diluted with dechlorinated tap water so that when 20 ml of the dilution were added to the petri dishes containing the juveniles final concentrations of 1 2 and 4 ppm of tcmtb were achieved in the 40 ml of fluid the control dishes received another 20 ml aliquot of lake arlington tap water all the dishes were adjusted to ph 7 when necessary the dishes were covered and held at 24 u00b0 c in a constant temperature room observations were made on the viability of the juveniles every two hours during the first 24 hours at 6 hour intervals during the next 48 hours and every 12 hours thereafter until either 100 mortality had been achieved or for 7 days viability was determined under a 30x microscope by observation of.