CHAPTER VI 

 ACCESSORY ORGANS OF HEARING 



We heave seen in the carps that from the anterior end of the primitive 

 lung, represented by the posterior sac, there grows a vesicle which 

 lies in the abdominal ca^aty. In two important families of present 

 da}' fishes, namely, the herring family or Clupeidse, and an African 

 family the Mormyridse, we find a duct given off from the swim- 

 bladder anteriorly, which divides into two finer ducts, and these 

 end in a vesicle or vesicles connected with the internal ear. The 



^ Ca/'e^nai l>lcJ-£ 



Fig. iji. — Head of Mormyrus Kannume (Worthington) to show 

 position of external auditory orifice. 



Diameter of eye -9 cm. Distance eye to ant. foramen TS cm. X Exposed portion 

 of sac '5 cm. F Vertical diam. foramen "7 cm. 



connection of the vesicle with the bladder is n(»t permanent in the 

 Mormyridge, but its rudiment remains ; whereas in the herring it 

 persists in the adult. In these famihes the connection with the 

 auditory organ is within the cranial cavity, so that there is no need 

 for a series of ossicles, as is present in the carps. We propose firstly 

 to describe the more simple and less controversial of these two 

 accessory organs of hearing. 



The African elephant fish or Mormyrus (Fig. iii) has a small 

 fenestra in the lateral wall of the skull which is closed by a very 

 thin osseous membrane loosely attached to the margin of the win- 

 dow, except at one point. Immediately beneath this lies an ovoid 



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