approved: Redacted for privacy Dr. Michael C. Mix The purpose of this study was to determine the effects of tritiated seawater (HTO) on selected developmental stages of the goose barnacle, Pollicipes polymerus. Barnacle embryos were cultured in Millipore cytology monitors with HTO concentrations of -5 -3 -1 1 0, 10 , 10 , 10 , and 10 p.Ci/ml. After 22 days, hatching was complete and the larvae and unhatched eggs were fixed in formalin. Criteria used in evaluating the effects of HTO on

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... t were morphological abnormalities, a "molting index" of stage I nauplii larvae and the mortality of eggs. Effects were seen at the lowest concentration when evaluated in terms of abnormalities and the molting index. Mortality, or viability of eggs, showed no clear doseeffect relationship. The Oregon Fish Commission aided this research by granting me a collecting permit and water temperature data were supplied by Allen McGie.