76 IOWA ACADEMY OF SCIENCES. 



THE MORPHOLOGY AND FUNCTION OF THE 

 AMPHIBIAN EAR. 



BY H. W. NORRIS. 



In the struggle for existence as individuals the Amphib- 

 ians, or Batrachians, seem to have a minor position. For 

 the most part of insignificant size, with poorly protected 

 bodies, and with retiring and inoffensive habits, these 

 forms which we know as toads, frogs and salamanders, 

 seem to be poorly adapted to maintain their species. 

 From what the paleontologist tells us, we may well believe 

 that the Amphibians as a class arose, flourished, and then 

 declined to their present insignificant proportions long 

 ago. It is because of the relationships of this group that 

 it is of profound interest to science. It forms a connecting 

 link, or rather a series of connecting links between the 

 strictly aquatic Vertebrates, the Fishes, and the terrestrial 

 forms. Presenting two distinct phases, a larval aquatic 

 and an adult terrestrial condition, it presents for our 

 observation the actual evolution of an aquatic, branchiate 

 form into a terrestrial pulmonate form. Furthermore 

 some forms retain the branchial organs throughout life, 

 while others hardly give us a hint of a much shortened 

 aquatic stage. This metamorphosis is not merely super- 

 ficial, but is accompanied by profound morphological and 

 functional changes. 



Experiments carried on in recent years, notably by Pro- 

 fessor F. S. Lee, have made it very probable that the ear 

 in Fishes is not an organ of hearing, but rather an organ 

 of equilibration. That it has this latter function in 

 all Vertebrates is very well known. It is then in the 

 Amphibia that the ear changes from an organ of equili- 

 bration alone to an organ of hearing, for it is certainly 



