162 THE STORY OF FISH LIFE. 



to pass the season of drought. These ponds, it 

 seems, abound with other fishes. It would be 

 interesting to know if these live in peace and 

 amity with the eels, or are gradually devoured 

 when other food supplies fail. 



We have yet a third very remarkable trans- 

 formation. This concerns the change which 

 certain gland-cells of the body in fishes undergo, 

 converting them into phosphorescent organs. It 

 is a well known fact that the slime secreted by 

 the skin glands of certain sharks is highly phos- 

 phorescent, and in this we have the foundation 

 for natural selection to work upon. If we pass 

 in review all the known species of phosphorescent 

 fishes, we shall find numerous gradations of in- 

 creasing perfection, leading up to exceedingly 

 complicated and powerful light-producing organs. 



Two kinds of phosphorescent organs are dis- 

 tinguishable. Qne of these takes the form of 

 peculiar eye-like, or lens-like bodies, arranged in 

 one or more rows down the sides of the fish's 

 body, forming, as Professor Hickson remarks, " a 

 series of miniature bull's-eye lanterns to illuminate 

 the surrounding sea"; the other, to quote the 

 same authority, is constituted by a series of 

 "glandular organs, that may be situated at the 

 extremity of the barbels (the filamentous organs 

 of touch round the mouth), or in broad patches 

 behind the eyes, or in other prominent places in 

 the head and shoulders." The light given off by 

 these organs, in some species, is said to shine 

 with a reddish lustre. 



These phosphorescent organs, it should be 

 noticed, are found either in fishes which inhabit 



