SESSION IV 221 FREMONT-SMITH: Do you want to tell us briefly that fascinating story about the olfaction and how they find their way? DONALDSON: This ia the work of Dr. Gorbman and associates. Dr. Gorbman is the chap who worked on the iodine uptake in the fish at Bikini (Reference 38). He has been doing memory pattern responses by taking the return salmon and immobilizing them, lifting the skull case off, putting probes in the olfactory lobes and then dropping water on the olfactory nares. The water may be from the "home stream, "' which gives a positive response, or a foreign stream, with a nega- tive response. Water samples collected from down river along the migratory path bring a positive response. FREMONT-SMITH: Down the river. DONALDSON: Yes, samples of water from down the river or up the river or some other place, or even tap water, and recording their memory response for this particular environmental stimulus. FREMONT-SMITH: The electrical activity to the environmental water. DONALDSON: Yea. AYRES: Is it an encephalogram technique? DONALDSON: Yea. FREMONT-SMITH: DONALDSON: What happens? The olfactory nares are sensitive to infinitesimally small amounts of "home" water. Dilutions of the "home" water continue to give positive responses. If, on the other hand, samples of water are obtained from 100 yards on up the watershed where the salmon haven't been, there's no response, TAYLOR: What happens if he takes them out of the water and gives them upstream water and downstream water and some nixed stream water? DONALDSON: This can be done. FREMONT-SMITH: It makes them very angry!