1892.] Contributions to the Anatomy of Fishes. 139 



BEFEKENCES. 

 (The page given is the one cited in the text.) 



Schmidt, 1862. ' Die Spongien des Adriat. Meeres,' pp. 25, 27. 



Schulze, F. E 1877. "Die G-attung Halisarca," ' Zeits. Wiss. Zool.,' 



vol. 28, p. 39. 

 "Die Familie der Chondrosidce" 'Zeits. Wiss. 



Zool.,' vol. 29, p. 102. 

 MerejkoYsky, C. de .. 1878. " Eponges de la Mer Blanche," 'Mem. Acad. St. 



Petersbourg,' vol. 26, 7, p. 32. 

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Plate 21, fig. 1. 



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Yosmaer, GK C. J. . .. 1885. 'The Sponges of the " Willem Barents" Expedi- 

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' Tijd. der Nederlandsche Dierkundige Vereeni- 



giiig,' Plate 14, fig. 8. 

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vol. 51, p. 474. 



XIII. " Contributions to the Anatomy of Fishes. II. The Air- 

 Bladder and Weberian Ossicles in the Siluroid Fishes." 

 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 NEWTON, F.R.S. Received June 9, 

 1892. 



(Abstract.) 



An abstract of the first part of this memoir, which dealt with the 

 structure and relations of the air-bladder and Weber's ossicles in the 

 Silurida3, was published in the Proceedings of this Society three years 

 ago ('Roy. Soc. Proc.,' vol. 46, 1889, pp. 309328). The present 

 contribution is a discussion of the physiology not only of this remark- 

 able mechanism, but of the air-bladder in general. 



There is a strong a priori probability that the Weberian mechanism 

 is physiologically related to one of the several functions that have 

 been ascribed to the auditory organ or to the air-bladder, but to which 

 of them is a question by no means easy to answer. A preliminary 

 difficulty to be encountered is the complex physiological character of 

 the two organs, and, apart from our imperfect knowledge of the 

 physiology of the several functions assigned to each, and especially in 

 the case of the auditory organ 'of Fishes, a further difficulty is 



