220 DASA 2019-2 FREMONT-SMITH: The most vulnerable period, AYRES: On the other hand, recovery can be more rapid. TAYLOR: Why don't they all die, is what I'm asking, LANGHAM: It's the dose rate. There's a lot of difference in giv- ing a dose in five minutes and over a hundred days. TAYLOR: [s ita factor cf 2? DUNHAM: yesterday. LANGHAM: Your monkeys all had lethal doses, as you showed Yes, if given in an hour or so. dose of the monkey is about 550 r. FREMONT-SMITH: The prompt lethal Please, gentlemen, don't have a private conversation because it makes it impossible, UPTON: I think a similar experiment has been performed on the mouse. [think I recall that Russell andassociates (Reference 44) could detect defects in mice exposed to dose levels of 25 r in the embryonic period whereas if they administered something like 13 r per day, continuously given over a 24-hour period throughout embryogenesis, they observed no effects, due presumably to the lower dose rate, DONALDSON: The most unusual aspect of this research is that the fish are tested over the entire life cycle. A major portion of their life span, of course, is spent in the highly competitive environment of the open sea, After the exposure period during incubation, the young fish are fed for about three months, until they have grown . to migrating size and have developed the ability to change from fresh to salt water, Then they are released to goto sea. After two or three years of active feeding in the sea they must be able to retrace their migratory pattern and "home" to the small pond on the University campus. ‘ There are surely many responsc patterns involved in the complex life cycle of the salmon, The final pinpointing of the "home stream" is now fairly well documented as a memorized olfactory response,