ON THE ANATOMY OP FISHES. 
G7 
they are principally tropical in habitat, or live in remote and inaccessible districts. 
Investigators at home are consequently dependent upon the exertions of collectors, 
who, as a rule, do not pay much attention to Fishes, and the relatively few species 
which do find their way to Europe are required for museum specimens. Fortunately 
for us we had the opportunity of purchasing the third series of the Siluroids collected 
by that eminent ichthyologist, the late Dr. Bleeker, who had amassed a magnificent 
collection of East Indian Fishes, amongst which the Siluridse were well represented. 
Subsequently we added to our collection what other specimens we were able to 
procure, especially African and South American species. 
The object of the present communication is to give the results of a detailed study 
of the morphology of the air-bladder, and “auditory” ossicles, and the associated 
skeletal modifications in 100 species of Siluridse, referable to 51 genera, and mainly 
belonging to Dr. Gunther’s sub-lamilies of Siluridse Homalopterse, S. Heteropterso, 
S. Proteropterse, and S. Proteropodes.'" Most of the species examined and described 
by us have either not been the subject of any recorded observations, or the accounts 
already given are too brief to be of much value ; in the few cases in which it is 
otherwise, references are given to what has previously been recorded. 
The physiological significance of the so-called auditory ossicles is still an unsettled 
problem, and one of the objects of our investigations was to ascertain how far the 
morphological variations of the mechanism, and of the air-bladder and auditory organ, 
in a large series of forms were able to throw any light on this difficult question, and 
failing a satisfactory solution by such means, we shall be satisfied if our results are 
regarded as furnishing the experimental physiologist with a sufficiently wide and 
accurate basis of morphological data. 
To our friend the late Dr. Francis Day, of Cheltenham, we are greatly indebted 
for the gift of numerous valuable specimens and for his kindness in identifying others. 
We greatly regret that he is not now living to receive this acknowledgment of our 
gratitude for his liberality and interest in our work. We are also indebted to Dr. 
Gunther for the acquisition of one or two species, and for his courtesy in allowing us 
every facility in examining the collection committed to his care ; and also to Dr. 
Sidney Lawrence, of Birmingham, for a small but valuable series of South American 
Siluroids collected by himself. We desire also to take this opportunity of thanking 
Professor J. H. Poynting, F.R.S., and Dr. W. W. J. Nicol, of the Mason College, 
for information and valuable criticism on certain physical points, and the Council 
of the Royal Society for grants to one of us from the Government Research Fund in 
aid of these investigadions.t 
* A preliminary abstract of tins paper appeared in ‘ Hoy. Soc. Proc.,’ vol. 4G, 1889. We may add as 
a personal explanation that this investigation was commenced by us several years ago, but for various 
unavoidable circumstances it had repeatedly to be laid on one side. 
t The figures ilhistrating this Paper were drawn from nature by our draughtsman, Mr. Henry 
Baenes, of Birmingham. 
K 2 
