120 BRAIN AND BODY OF FISH 



sufficient frequency to produce sound. These waves are, therefore, 

 perceived by the lateral line organs and as they are distributed 

 along a long base the wave would be received in varying intensity 

 by organs situated at a distance from each other. In this way a 

 series of observations made by a predatory fish of the waves pro- 

 duced by its prey would enable its position to be plotted, in the 

 central area of the brain, which we have given reasons to suggest, 

 is the acustico-laterahs lobe. 



These facts relating to the hake are of still greater importance 

 in the hunting equipment of the scabbard fish and of other deep sea 

 fish ; it is true that these fish have very large eyes but the optic 

 lobes are comparatively small ; however, the acoustic tubercles are 

 very large. The eyes are large in order to obtain the maximum 

 of light in the darkness of the deep, and the optic lobes are of little 

 use until the last act of the drama and the seizing of the prey. The 

 lateral line organs may, therefore, be the means of guiding the 

 attacking fish in pursuit of prey, and this accounts for the functional 

 enlargement of the acoustic tubercles. It must also be noted that 

 the scabbard fish is of great length, and this gives it a long base for 

 their observations and increases the efficiency of the lateral line 

 organs. 



