232 OF DEEP-SEA FISHES IN GENERAL 



the species the mucous-canal-systems of the head and 

 lateral line are surprisingly developed, and it is 

 thought with good reason that the mucous thus so 

 copiously secreted is luminous. But many of the 

 species also possess special phosphorescent organs : 

 these may be scattered, but are more commonly 

 arranged in definite lines along the mucous canals of 

 the head and trunk, and they are of every degree of 

 perfection, from a simple pearly patch of skin up to a 

 structure having a strong resemblance to a miniature 

 ''bull's-eye." These luminous organs, it should be 

 mentioned, are sometimes used, not as search-lights, 

 but as lures to attract prey. Such is supposed to be 

 their function in the case of the deep-sea Anglers, 

 where the light is placed at the tip of the modified 

 fin-ray which in other Anglers forms the rod and 

 bait. 



Another result of the darkness, or dimness, of the 

 depths is that many deep-sea fishes, especially those 

 species in which the eyes are small, are thrown back, 

 in compensation, upon the sense of touch, and this 

 has in some cases led to an extraordinary develop- 

 ment of some of the fin-rays, which may even be 

 transformed into long antenna-like feelers, by whose 

 means, as Moseley has expressed it, the possessor 

 gropes its way in the dark, like a blind man with a 

 stick. There seems also to be some reason to believe 

 that, in addition to any other functions which it may 



