IOWA ACADEMY OF SCIENCES. 77 



true that many of the toads and frogs have very acute 

 auditory powers. We are not able to show experimentally 

 whether there are any Amphibians in which the sense of 

 hearing is wanting, since the bony skull and the small size 

 of the ear capsule almost preclude the possibility of accu- 

 rate experiments such as have been performed upon the 

 Dog-fish. But we are justified, it seems to me, in basing 

 some conclusions on the study of the structure of the 

 Amphibian ear. 



In the general form and relationships of its parts the 

 inner ear, or labyrinth, of Amphibia, is essentially fish- 

 like. The only important new structures are the pars 

 basilaris, and closely associated with it the perilymphatic 

 canal, the two structures that combine in the higher 

 classes of Vertebrates to form that complicated organ, the 

 cochlea. In Proteus, Necturus, Siren, Amphiuma, and 

 presumably in that blind branchiate form, Typhlomolge, 

 from the subterranean streams in Texas, the pars basilaris 

 is wanting. In all other Amphibia, as far as investigation 

 has gone, it is present. In the Ilrodela, with the exception 

 of Amphiuma, in which it is absent, it is a small insignifi- 

 cant recess in the lagena and contains a small sense-organ. 

 In the Anura it becomes a distinct part of the labyrinth 

 with a well developed sense-organ, closely related to the 

 perilymphatic canal. In the Anurous Amphibia there also 

 occurs a well developed middle ear, or tympanum, a struc- 

 ture entirely wanting in the other members of the class 

 and in the Fishes. 



Is the ear in the tailed amphibians an organ of hearing? 

 This cannot as y6t be answered very satisfactorily. A dis- 

 tinct vocalizing apparatus is lacking in all but the Anur- 

 ous Amphibia. Salamanders are notably silent creatures. 

 John Burroughs, I believe, says that the Red Eft, that 

 immature terrestrial form of Diemydylus viridescens, pro- 

 duces a musical sound, but it is undoubtedly not a true 

 vocalization. This lack of vocalizing powers in the Sala- 

 manders makes it very probable that they are defective in 

 hearing. There being no tympanum present the ear cov- 

 ered up by bone and muscle, cannot well respond to 



