How to obtain it. 269 



be held that with a low temperature they eat but little, and with a 

 high one they eat greedily. There are many other influences at 

 work, however, which cause them to eat more or less freely, but 

 which can hardly be discussed here. It is well known that during 

 the summer months they accumulate a great amount of fat, and 

 thus they are better enabled to bear the starving which they get 

 during the winter. 



There has been a great deal of controversy as to whether 

 trout can hear. The ear of a trout may be briefly described as 

 an internal organ that is tolerably well developed, and is situated 

 within the cranial cavity. But it has no tympanum, nor yet any 

 tympanic chamber. That a trout cannot hear in the ordinary 

 way is, I think, beyond any doubt, as the ear is not constructed 

 for that mode of hearing. But trout are exceedingly sensitive to 

 vibration, and any sound made beneath the water, or even in the 

 earth, as for instance in blasting a rock, may be transmitted by 

 vibration, and the fish in this case would be immediately sensible 

 that a disturbance had taken place. 



The labyrinth of the ear is well developed, but the external 

 orifice is closed, and we know what is the effect on ourselves if 

 we, for instance, put our fingers in our ears when anyone is 

 talking. I once tried some experiments with fish with regard to 

 their sense of hearing, and I came to the conclusion that trout 

 could not hear sounds made in the air, provided no agitation 

 of the water occurred. The same applies to some other fishes. 

 Amongst others I operated upon a shoal of herrings (Chtpea 

 harengus) in a tank. Moving my hand to and fro close to the 

 glass, I got the fish so accustomed to the sight that they took no 

 notice of it whatever. But the moment my hand smacked against 

 the glass they scattered in bewilderment. I tried shouting and 

 making noises, but they apparently did not hear at all. Now, 

 there is in many fishes a connection between the internal ear and 

 the air bladder. In the herring, for instance, we find at the fore- 

 end of the bladder two very narrow tubes or ducts, which connect 

 or at least come into exceedingly close contact with the organ of 

 hearing, passing right through the skull, and apparently connecting 

 with the labyrinth of the ear. 



There is also in the herring a very curious connection between 



