86 PARKER— A CRITICAL SURVEY OF 



translation from an air medium to a water medium as they do in 

 air-inhabiting vertebrates. When, therefore, as occasionally 

 happens, a fish takes up with a temporary residence in the air, it 

 should not be expected to be very responsive in this situation to 

 sounds. This seems to be the case with Periophthalmns phya, 

 which often deserts the water for the shore and which, when in the 

 air, is apparently quite deaf even to the report of a shotgun (John- 

 stone, 1903, p. 300). It is only after the development of some form 

 of translating apparatus, such as an ear-drum and a middle ear, that 

 it would be fair to expect such animals to show much response to 

 sounds in the air. Organs of this kind characterize the ears of air- 

 inhabiting vertebrates and represent a means of overcoming an 

 auditory obstacle which fishes have not had to meet, for, as has 

 just been made clear, there is not the least ground for assuming that 

 from a physical standpoint water-inhabiting animals find any im- 

 pediment to hearing. 



It is a well-known fact that sounds produced in the air penetrate 

 water to only a very slight degree and, conversely, that sounds gen- 

 erated in the water pass out into the air only to a correspondingly 

 limited extent. The ordinary surface between air and water is an 

 excellent reflector of sound. Parker (1911&, p. 4) found that even 

 •the loud noise from a motor boat was only faintly heard by an ob- 

 server who dove close to the boat and Watson (1914, p. 393), when 

 under four feet of water, was unable to hear the report of a re- 

 volver discharged in the air overhead. It is, therefore, not surpris- 

 ing that FuJiduhis, though very sensitive to sounds, did not respond 

 to the report of a saluting charge of two pounds of gun-powder ex- 

 ploded from a six-pound howitzer until the fish was within thirty 

 feet of the muzzle of the gun when to the human ear the sound was 

 deafening (Parker, igiib, p. 8). These conditions were fully ap- 

 preciated by Bateson (1890, p. 251) when he remarked apropos of 

 certain tests on pollack: "As might be expected, none of the fishes 

 were seen to take notice of sounds made in the air." Such sounds, 

 as has already been shown, fail in large part to enter the water, being 

 mostly reflected from its surface back into the air. 



It is probably due to this circumstance, rather than that fishes 

 do not hear, that the tests of a number of investigators who used 



