580 SCIENCE PROGRESS 



One can only suppose, as has been suggested by some physio- 

 logists, that it is a more or less direct result of the greater 

 share taken in equilibration among higher vertebrates by sense 

 organs, other than the ear, of improved efficiency and power of 

 co-ordination. 



On the other hand, when we consider the fact that in fishes 

 there are only those parts of the ear present to which, by 

 common consent, powers of equilibration alone are ascribed, 

 we are confronted by the interesting question whether it is 

 to be expected or rather whether there is any evidence to 

 show that fishes have any true sense of hearing, seeing that 

 in their ear there is no structure at all comparable to that by 

 which this function is performed in terrestrial vertebrates. 



This is a question that has exercised the minds of naturalists 

 since very early days. It was one of the problems that engaged 

 John Hunter * in the eighteenth century but it appeared then 

 far more simple of solution than now, for it was taken for 

 granted that, if fish were sensitive to noises, the labyrinth, from 

 its resemblance to the human ear, without question must be the 

 organ affected; further, no distinction was drawn between 

 coarse mechanical vibrations that can be felt and true molecular 

 sound vibrations that can only be heard. 



Hunter attempted to solve the problem as presented to 

 him by a very simple experiment and was quite satisfied with 

 the result. 



While serving with the army in Portugal, he chanced to be 

 watching a pond in which Gold-fish were swimming. To test 

 their sensitiveness to sound, he got a friend who was with him 

 to fire a gun screened from the fish by some bushes. No sooner 

 was the gun fired than the fishes .vanished into the mud at the 

 bottom of the pond. 



Now this and similar experiments show that fish are sensitive 

 to shock or jar but that is all. They give no clue to their power 

 of true hearing nor as to whether the labyrinth is the organ 

 affected and if so what part of it is the actual receptive organ. 



Since Hunter's day, experiments have been carried out with 

 the object of answering these questions but so far with per- 

 plexing and inconclusive results. 



A few abstracts from some recent work on the subject will 

 show the position. 



1 Hunter, Phil. Trans. 72, 1782, p. 379. 



