28o Journal of Comparative Neurology and Psychology. 



nects it with the ear-sac ; and they differ from mammals, to 

 mention only the two chiefly significant features, in that they 

 lack an organ of Corti and a pinna. Anatomically the fish 

 and the mammal represent respectively the simplest and 

 most complex conditions in the vertebrate auditory 

 series. It is not hard to see why investigators should 

 have been interested first and chiefly in the problems 

 of the existence and state of development of the sense 

 of hearing in those vertebrates which have labyrinth organs 

 only (fishes), and in those which have also an organ of Corti 

 (mammals, for example). In the case of the former, lacking as 

 they do all external evidence of an auditory organ as well as 

 the organ of Corti, which is the recognized special organ of 

 hearing in the mammals, it it is not at all surprising that con- 

 siderable doubt should have existed at various times concerning 

 the existence of a sense which may properly be called hearing. 

 Since frogs stand between fishes and mammals in the vertebrate 

 auditory series, they would naturally be expected to hear in 

 case fishes do. Attention has long centered where the exist- 

 ence of hearing seemed most doubtful, and it will be profitable 

 for us, before taking up the special evidence of hearing in the 

 frog to note the result of the most recent study of hearing in 

 fishes. 



The history of the investigation of the functions of the ear 

 in fishes is a curiously interesting and instructive chapter in the 

 progress of sense-physiology, for it exhibits the development of 

 scientific method, as well as the gradual increase in the scope 

 and exactness of knowledge. A brief historical sketch of the 

 subject is given by Parker^ in a paper on hearing and allied 

 senses in fishes. In this excellent contribution to the subject 

 the author, after defining hearing "as that sensory activity 

 resulting from a stimulation of the ear by material vibrations" 

 (p. 46), states that Fundulus and several other fishes, which 

 when normal respond definitely to vibrations of a frequency of 

 128 per second transmitted directly to the water of an aquarium, 



^Hearing and Allied Senses in Fishes. Bu//. U. S. Fish Com. 1902. pp. 45-64. 



