Dr. Hubbs was inclined to attribute whale noises to movement of 

 air back and forward in the lungs, and it was thought possible that they 

 ma}^ at times exhale below the surface to produce a noise, although in 

 ■ that case air bubbles would be observed accompanying the exhalation. 



Dr. Hiatt remarked that divers can communicate as far as 10 ft. 

 away. It had previously been maintained that " ship worms " could be 

 heard working in the hulls, but Dr. Johnson attributed this actually to 

 Crangon shrimps. 



In answer. to Dr. Hiatt, who inquired whether the high pitch whale 

 note might be that of a calf, it was doubted whether calves were present 

 with the school of hump-backs. Dr. Hubbs pointed out that it had 

 been determined at Scripps that whales have obviously some means of 

 communication. 



Many of these sounds were stated to be within human audible range, 

 such as those of croaking fishes. Others, such as some of the crustacean 

 sounds and the high frequency porpoise sounds, were outside the range 

 of audibility. In fishes, sound is perhaps associated with the breeding 

 cycle, sound-producing organs being confined in some cases to one sex 

 only. Dr. Hubbs indicated that Silurid cat-fishes have stridulating 

 organs on the pectorial spine. 



Mr. Powell raised the question of shell-fish noises on New Zealand 

 estuaries. He stated that the clicking noises observed about dusk were 

 perhaps attributable to cockles closing their valves suddenly. Dredgings 

 over estuaries had indicated an absence of snapping shrimp. Dr. Johnson, 

 however, discounted the theory that either oysters or cockles produced 

 the noise, and Mr. Morton stated that on Auckland Harbour estuaries he 

 has found by digging specimens of Crangon novae-zelandiae associated 

 with cockles and producing a noise like the fall of hailstones. 



Dr. Hiatt inquired whether noises were produced by skin friction in 

 swimming. No work had been done, but Dr. Johnson thought the 

 effects would probably be of minor importance. 



Stream lining is well developed in fishes. Tail whipping and muscular 

 movements might, however, produce sound. Dr. Hubbs cited the 

 scarcely perceptible hum of Leptocottus, and Dr. Johnson referred to 

 that of grunt-fish and the small alligator fish. There was also cited the 

 clicking sound made by some shore crabs in exuding bubbles from the 

 mouth. 



Dr. Emery inquired whether perhaps sea mammals might make use 

 of noises for echo ranging in the pursuit of fish. It was stated also that, 

 on the inverse side, advantage might be taken of artificially produced 

 noises or recordings to frighten away fish from specific localities during 

 T.N.T. depth chai^ge wojk, during which fish mortality was heavy. It 

 was suggested, further, that fish might be attracted by the reproduction 

 of suitable noises. 



Dr. Brunn gave an account of the detection of dolphin schools during 

 the use of high-frequency echo-sounding apparatus. He stated that a 

 school of 100 to 125 were observed smacking the water with their tails 

 with great vigour. 



A discussion followed on the occurrence of auditory organs and sound 

 receptors in fish. Dr. Brunn emphasized that fish are able to detect 

 half-tones, as had been established by the production of conditioned 

 reflexes in which a series of auditory effects differing by half-tones had 

 been associated with disagreeable and palatable food substances. 



208 ■ 



