106 Book or the Black Bass. 



aquaria, but to those in open water as well, and in refer- 

 ence to the latter condition he says : 



" The sound, therefore, was as unrestricted as that which natu- 

 rally reaches these fishes. On experimenting with normal fishes, 

 fishes without ears, and those with insensitive skins, results were 

 obtained essentially like those observed in the aquarium, and I 

 therefore concluded that the restriction of the water in the 

 equarium played no essential part in the results obtained from 

 that apparatus. There is, thus, good reason to believe that 

 Fundulus heterocUtus not only hears, but that for it hearing is 

 a normal process." 



Mr. Parker means by "fishes without ears, and those 

 with insensitive skins," fishes in which the cutaneous and 

 auditory nerves were severed. His summary of the results 

 of his experiments is as follows : 



" 1. Normal Fundulus heterocUtus reacts to the sound waves 

 from a tuning fork of 128 vibrations per second by movements of 

 the pectoral fins and by an increase in the respiratory rate. It 

 probably also responds to sound waves by caudal-fin movements 

 and by general locomotor movements. 



" 2. Individuals in which the eighth ( auditory ) nerves have 

 been cut do not respond to sound waves from the tuning-fork. 



" 3. The absence of responses to sound waves in individuals 

 with severed eighth nerves is not due to the shock of the operation 

 or to other secondary causes, but to the loss of the ear as a 

 sense organ. 



" 4. Fundulus heterocUtus therefore possesses the sense of 

 hearing. 



" 5. The ears in this species are also organs of prime impor- 

 tance in equilibration. 



" 6. Normal Fundulus heterocUtus swims downward from the 

 top of the water and remains near the bottom when the aquarium 

 in which it is contained is given a slight noiseless motion. 



" 7. Individuals in which the nerves to the lateral-line organs 

 have been cut will swim upward or remain at the top while the 

 aquarium is being gently and noiselessly moved. 



