G6 
PROFESSORS T. W. BRIDGE AND A. C. HADDONJ 
and comparative examination of any considerable number of genera, and, at the same 
time, to deal with the various modifications which pertain to the air-bladder, auditory 
organ, and skeleton as correlated and mutually dependent factors. With regard to 
papers on such special points as the nature of the “ complex ” vertebra and the 
homologies of the Weberian ossicles, reference may be made to the contributions of 
Baudelot (1), Grassi (17), and Nusbaum (29), and to a recently published and 
valuable paper by Sorensen (37), which treats of certain skeletal modifications, not 
only in the Ostariophysese in general but in other Teleostei. Of papers dealing with 
other special points, the contributions of Hasse (19) and Nusbaum (/oc. cit.) to the 
anatomy of the auditory organ must also be mentioned. Of individual families, the 
Siluridse have received but little attention. Sagemehl’s paper deals mainly with the 
air-bladder of the Characinidse. The papers of Grassi, Baudelot, and Nusbaum relate 
almost exclusively to the Cyprinidae. The valuable observations of Sorensen, while 
more extensive as regards the families included within the range of his investigations, 
are nevertheless restricted to certain special features, and, apart from the develop- 
ment of ossifications in its walls, have but scanty reference to the air-bladder, or to 
the Weberian ossicles, or to the auditory organ in the relatively few Siluridee 
described by him. Weber {loc. cit.) himself only described the air-bladder and the 
ossicles which bear his name in a single species [Silurus glanis). Johannes Muller, 
in his various contributions to the Berlin Academy during the years 1843-45, added 
somewhat to our knowledge of these structures, and nptably by his discovery of the 
“ elastic-spring ” apparatus, 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 Siluridae, or to the auditory ossicles. 
Beissner (32) has given a fairly complete account of the singular bone-encapsuled 
air-bladder of Rhinelepis, but among the most valuable of recent contributions to this 
branch of vertebrate morphology are the papers by Professor Bamsay Wright 
relating to the aberrant Siluroid Hypophthalmus (44), and to the more normal North 
American species Amiurus catus (42, 43), to which reference will subsequently be 
made. In this connexion reference may also be made to the numerous scattered 
references to the air-bladder of the Indian Siluridse contained in the papers of the 
late Dr. Francis Day (9, 10), which, although often too brief, in several instances 
at any rate are valuable as throwing some light on the degenerate condition of that 
organ in certain rare abnormal forms. 
It is remarkable that this important family of Fishes has so little occupied the 
attention of morphologists, especially when we take into consideration the interesting 
modifications which its various members have undergone, and the fact that in this 
family the air-bladder and “auditory” ossicles are subject to greater variations, and 
are more highly specialized than in any other group of Ostariophysese. Probably the 
main reason why the Siluridm have been so much neglected is due to the fact that 
