24 THE FAUNA OF THE DEEP SEA 



phosphorescence. Most fish possess, as is well 

 known, a very acute sense of smell, and it is very- 

 probable that they avoid such nets on account of 

 the putrid odours of the dead animals that remain 

 attached to them. 



Nor is there much strength in the further 

 argument that it can hardly be possible that there 

 can be an amount of phosphorescent light regularly 

 evolved by the few deep-sea animals, having this 

 power, sufficient to cause any general illumination, or 

 powerful enough to have influenced, over the whole 

 ocean, the evolution of complex eyes, brilliant and 

 complex protective colours, and complex commensal 

 adaptations. 



We have no sound information to go upon to be 

 able to judge of the amount of light given off by 

 phosphorescent animals at the bottom of the deep sea. 

 The faint light they show on deck after their long 

 journey from the depths in which they live to the 

 surface may be extremely small compared with the 

 light they give in their natural home under a pressure 

 of 2 J tons to the square inch. The complex eyes 

 that many deep-sea animals exhibit were almost 

 certainly not evolved as such, but are simple modifi- 

 cations of eyes possessed by a shallow-water ancestry. 



