72 PARKER— A CRITICAL SURVEY OF 



Some fishes show considerable divergence from the plan of struc- 

 ture just laid down. Aside from amphioxus, which possesses no 

 ears at all, the cyclostomes exhibit the simplest and probably the 

 most primitive type of this sense organ. In these fishes each ear 

 consists of a single sac with never more than two semicircular canals 

 corresponding very probably to the anterior and the posterior ver- 

 tical canals of the higher vertebrates. There are three sense organs, 

 a crista acustica for each of the two canals and a macula acustica 

 communis on the wall of the sac. In all higher fishes each ear-sac 

 is double, as already described, consisting of a sacculus and a utricu- 

 lus with its three semicircular canals. This type of ear possesses 

 ordinarily the seven sense organs already enumerated, the macula 

 acustica neglecta being, however, occasionally absent. In the elas- 

 mobranchs the utriculus and sacculus of a given ear communicate 

 freely with each other through a relatively large opening. In the 

 teleosts and other higher fishes a narrow tube, the utriculo-saccular 

 canal, may connect these two parts, or they may be quite disconnected 

 and separate. Of the thirty-three species of teleosts reported on by 

 Retzius, eleven possessed a well-developed utriculo-saccular canal, 

 two showed traces of it, and twenty were without the least sign of 

 it, though in embryonic stages they presumably possessed it. These 

 are the chief facts in the comparative anatomy of the ears of fishes. 

 As the terminology shows, these organs were regarded as organs of 

 hearing and this opinion was the prevailing one among scholars of 

 the last century. It has been more or less tacitly assumed in the 

 more important text-books of that period such as Owen (1866), 

 Wiedersheim (1883), Gegenbaur (1898), and others. 



The first noteworthy opposition to this opinion came from de 

 Cyon (1878). This investigator, in his study of the function of the 

 semicircular canals in vertebrates, made the observation (p. 93) that 

 lampreys did not respond to sounds and that after their internal ears 

 had been removed, in itself a relatively simple operation, they ex- 

 hibited great disturbances in locomotion. These disturbances were 

 to be observed seven weeks after the operation and were presum- 

 ably permanent. De Cyon, therefore, concluded that the cars in 

 this primitive fish were concerned with responses to spacial relations 

 and had nothing to do with hearing. This opinion was supported 



