As indicated in UWFL-34 (2) future work will include, in addition to snail egg studies, a comparison of the relative biological effectiveness of soft and hard X-rays and C0? gamma rays using agar plates of Chlorella. B. Radiobiological studies of fishes Results of the experiment on the effects of X-radiation on early stages of development of salmonoids have been reported in UWFL-34. The report on the preliminary experiment on the effects of X-rays on six developmental stages of rainbow trout, Salmo gairdnerii, involving a total of approximately one thousand fish, portions, is being written. Mortality, growth, body pro-~ fin ray number and color (parr marks) have been studied and found to be altered by comparatively low doses. Teratological effects on external features are now being ana- lyzed. This material will then be summarized and compared with radiation effects on other animals. The second salmonoid experiment in progress on Oncor- hynchus kisutch (silver salmon) is a much more complex study on effects of X-rays on 17 developmental stages involving a total of approximately 11,500 fish. analyzing the skeletal system This study will include (by radiographs) developed subsequent to X-radiation as well as making observations similar to those made in the trout.