IOWA ACADEMY OF SCIENCES. 



HOMOLOGIES OP THE CYCLOSTOME EAR. 



BY H. W. NORRIS. 



The ear of the Cycles tomata has until recently been consid- 

 ered so peculiar as to render it difficult to explain its relations 

 to the typical Vertebrate ear. Then again, the diversity of 

 structure in the auditory orga,n of the Cyclostomes themselves 

 renders the task of homologizing the various parts somewhat 

 uninviting. 



Our exact knowledge of the structure and relations of the 

 ear of the Cyclostomata begins with the researches of KeieP, 

 in 1872. His predecessors had assumed that the auditory organ 

 of the Cyclostomata was a thing sui generis, hence most of their 

 observations were defective. Ketel was the first to attempt 

 to find a fundamental type of the vertebrate ear. While the 

 results of his studies in that direction did not find ready accept- 

 ance, nevertheless, in the light of most recent investigations, 

 we see that his conclusions were essentialiy correct. In the 

 light of zoological knowledge tAventy years later, his opinions 

 would have seemed not only reasonable, but they would have 

 been considerably modified from their original form. Johannes 

 Miiller" in 1836 discovered the semicircular canals in the ear of 

 Petromy zon, and that they were only two in number. DameriP 

 in 1800 claimed to have found the canals, but his statements 

 are extremely vague. Other observers, PohP, Weber\ Blain- 

 ville^ Rathke' and Breschet^ had denied the existence of the 



1 Ueber das Geliorogan der Cyclostomen— Basse Anat. Studien, 1872. 



2 Ueber den cigeiithumlichen Ban des Gehororgans bei den Cyclostomen. Fortsctz 

 d Vergl. Anat. d. Myxinoiden in Ahli d. K. Akad. d Wissen. Berlin, 1836. 



3 Anatomie des Lamproies Memoires d anatomic comparee. Paris, 1800. 

 ^Expositis generalis anatomica organ! auditus per classes animalium. Vindo- 



bonae, 1818. 



SDe aure et auditu hominis et animalium. Leipzig, 1820. 



6De I'organisation des animaux ou Principes d'anatomie comparee. Paris, 1822. 



7 Bemerkungen uber den inneren Bau der Pricke. Danzig, 1826. 



SRecherches anatomiques et physiologiques sur I'organe de I'ouie des poissons.. 

 Acad, des Sci Sava7is Eirangers. 1838. 



