532 PKOF. T. W. BRIDaE OK THE 



logical points in connection with the latter Fishes, I must again 

 emphasize my conviction that physiological conclusions drawn 

 solely from anatomical data must be regarded as little more than 

 tentative and provisional suggestions. 



At the conclusion of his account of the mode of connection 

 between the air-bladder and the auditory organ in certain species 

 of Sparus, "Weber (op. cit. p. 72) states his views as to the 

 physiological value of the connection in the following words: — 



" Prima utilitas hsec est, ut tremoros soniferi aquae toti 

 piscium corpori communicati, a vesica natatoria elastica recipi- 

 anter, in se coUiquantur, et in membranam, fenestram vestibuli 

 ossei obducentem, transferantur, cuius tremoros liquorem, cavum 

 cranii replentem, movent itaque vestibulem membranaceum 

 ipsum, ab aqua cranii circumdatum, afficiunt ad quam quidem 

 utilitatem vesica natatoria, quippe quae singulis costis affixa est, 

 aptissima videtur." 



On this theory the air-bladder, by reason of its connection 

 with the auditory organ, becomes a physiological accessory to 

 audition, in addition to its usual and normal function as a hydro- 

 static organ. 



In discussing "Weber's view of the auditory function of the air- 

 bladder and "Weberian ossicles in the Ostariophysese, it was 

 pointed out by Bridge and Haddon (2. p. 276) that, assuming 

 sound-waves to be transmitted from the air-bladder to the 

 auditory organ by these ossicles, the fact that such stimuli 

 would, in the first instance, affect certain median and unpaired 

 structures common to both auditory organs (sinus impar and 

 sinus endolymphaticus) involved the difficulty that the mem- 

 branous labyrinths of opposite sides of the head would be affected 

 with equal intensity and simultaneously, and, consequently, as 

 no differential stimulation took place, the Fish would be incapable 

 of appreciating the direction of the sound. 



Sorensen (10. pp. 185-186), in attempting to mitigate the force 

 of this criticism, remarks : — " As far as I can see this is the only 

 real objection that can be made against the theory of "Weber. 

 But I do not judge it to be of great importance. If this 

 objection were absolutely valuable, no human being would be 

 able to decide if a sound arises before or behind him when the 

 direction of the sound coincides with the symmetrical plane of the 

 body ; and this, however, we are able to decide. And, would 

 not this objection be just as valuable if you presume the sound 

 not to be transmitted to the ear through the air-bladder? Are 



