1889.] Contributions to the Anatomy of Fishes. 309 



VII. " Contributions to the Anatomy of Fishes. I. The Air- 

 bladder and Weberian Ossicles in the Siluridse." By 

 T. W. Bridge, M.A., Professor of Zoology in The Mason 

 College, Birmingham, and A. C. Haddon, M.A., Professor of 

 Zoology in the Royal College of Science, Dublin. Com- 

 municated by Professor A. Newton, F.R.S. Received 

 June 12, 1889. 



Weber, in his classical memoir entitled ' De Aure et Audita 

 Hominis et Animalium. Pars. I. — De Aure Animalium aquatilium,' 

 published in 1820, was the first to show that in certain families of 

 Physostomous Teleostei, which were subsequently grouped together 

 under the name of Ostariophyseae by the late Dr. Sagemehl, there 

 exists a peculiar connexion between the membranous labyrinth of 

 the internal ear and the air-bladder by means of a chain of movably 

 interconnected "auditory" ossicles. Of the four families (Gymnotida?, 

 Characinidee, Grymnarchidaa, and Siluridae) in which this singular 

 mechanism is present, the Siluridaa have received but compara- 

 tively scanty attention since the publication of Weber's paper. 

 Weber himself only described the air-bladder and auditory ossicles 

 of one species (Silurus glanis). Johannes Miiller, in his various com- 

 munications to the Berlin Academy during the years 1843—45, added 

 somewhat to our knowledge of these structures, and notably by his 

 discovery of the springfederapparat ; but Muller's attention was 

 mainly directed to the grosser features in the anatomy of the air- 

 bladder to the entire exclusion of all but the slightest reference to 

 the important skeletal modifications which are associated with the 

 peculiar structure of that organ in the Siluridaa. Reissner has given 

 a fairly complete account of the bone-encapsuled air-bladder of 

 Rhinelepis, but by far the most valuable of the more recent contribu- 

 tions to this branch of vertebrate morphology are the papers by 

 Professor Ramsay Wright, relating to the aberrant Siluroid 

 Hijpothalmns, and to the more normal North American species, 

 Amiurus catus. In his papers on Amiurus, Professor Wright was not 

 only the first to describe the fusion of the second, third, and fourth 

 vertebras in the formation of wdiat we have termed the "complex 

 vertebra "—a fact which could hardly have been discovered except 

 through embryological evidence — but was also the first to give an 

 accurate account of the skeletal relations and attachments of the air- 

 bladder in any one Siluroid. 



In this preliminary communication we propose to state briefly the 

 results of our investigations into the various modifications which 

 the air-bladder and the "auditory ossicles" undergo in ninety-two 



