100 The Life Story of the Fish 



silhouette. It is probable that it is only when a lure is 

 beneath the surface that its color can be told. 



Finally we come to a question which has little to do with 

 the eyes except that, in man's mind and through man's habit, 

 it is associated with them. Do fish sleep? The answer is, Yes 

 — at least certain species — if the opinions of the majority of 

 scientific observers are to be accepted. After all, why should 

 the mere fact that a fish has no lids with which to close its 

 eyes make us question that it sleeps? We have no way of 

 closing our ears, and yet we sleep. Sleep is a state in which, 

 among other things, our conscious minds are temporarily 

 disconnected from the outside world. If we can sleep in spite 

 of the messages which our ears are continually sending in to 

 headquarters — and which, in a large city, are neither few 

 nor faint — why cannot a fish sleep in spite of the messages 

 which its eyes send in? It is all a question of what you are 

 accustomed to. Fish do sleep. Some sleep suspended in the 

 water, some rest erect on the bottom, some lie on their sides 

 on the bottom. The "Slippery Dick" {Iridio bivittata)^ a 

 small Bermuda wrasse, literally goes to bed and pulls the 

 covers over its head. Put one into a tank with a sand bottom, 

 and go back at night and switch on a light, and there is no 

 fish to be seen. You have to look very closely to find the 

 small crater in the tiny volcanic peak of sand, quietly rising 

 and falling as your fish breathes, which marks the gill open- 

 ing. And if you watch this disappearing act, you find that 

 it is almost like a magician's trick: the fish dives slantingly 

 into the sand, gives a couple of strong wiggles with its tail, 

 and is lost to sight. 



As usual, the sharks require a separate paragraph. In 

 three particulars, their eyes differ from those of the bony 

 fishes. The lens is set for distant rather than near-by vision, 

 and in some species cannot be moved. The amount of light 

 entering the eye can to a certain extent be controlled. And 



