I THE COLOURS OF ORGANISMS 23 



but the observations are too limited for any con- 

 clusion to be drawn. 



With regard to phosphorescence in general it 

 appears to be most common in the relatively simple 

 organisms of the pelagic fauna, and next to these in 

 the abyssal fauna. If, as there seems much reason 

 to believe, it depends upon processes of oxidation, 

 its presence in the deep-sea forms is very remarkable. 

 The phosphorescent organs of the deep-sea forms, 

 especially the fishes, occur most frequently in con- 

 nection with nervous organs, especially with those 

 delicate tactile processes so characteristic of these 

 animals. A good example of this is found in the 

 luminous " lures " of the deep-sea fishing frog. The 

 statement that this form has adopted the salmon 

 poacher's method and does its fishing by means of a 

 luminous lure, seems at first sight to demand a teleo- 

 logical explanation, but when we remember that the 

 lures are greatly developed tactile organs the fact 

 that they are luminous is less inexplicable, in origin 

 at least. The whole subject of the phosphorescence 

 of abyssal forms is exceedingly puzzling. We are all 

 familiar with the pictures of the abysses of the ocean, 

 of the chill darkness illuminated by fitful gleams of 

 phosphorescent light, but it is difficult to decide how 

 far these representations are justifiable. It is a 

 somewhat obvious remark that no one has seen this 

 lower world, but is one which is perhaps not altogether 

 unnecessary. Many deep-sea organisms phosphoresce 

 when brought to the surface, but there is no proof 

 that they do so under the ordinary conditions of their 

 life. Has the increased amount of oxygen in the 

 surface waters no intensifying effect ? Then also the 



