v GROWTH, MIGRATIONS, FOOD AND HABITS 129 



In its younger and smaller stage this luminous shrimp has been 

 taken in numbers at the surface of the sea, in the North Sea, in 

 the Firth of Clyde, and off the coast of Cornwall. But in the 

 adult condition it has only been taken at considerable depths ; 

 it is then about i^ inches long. It does not, however, when adult 

 crawl upon the bottom ; it is a restless swimmer and requires no 

 support, but is only found near the bottom. This animal is a 

 constant inhabitant of certain deep gullies in the Firth of Clyde, 

 where the depth is about 70 fathoms, and where it can always be 

 captured in some numbers by towing a shrimp trawl at consider- 

 able speed. Recent observations have shown that Loch Fyne 



FIG. 82. A luminous Shrimp (Nyctiphanes] ; after G. O. Sars. 



herring feed largely on this crustacean, a fact which proves that 

 herring may descend to considerable depths. 



It is a well-known story that some Hindoo religion taught 

 that the world rested upon the back of a great elephant, and 

 the elephant stood on the back of a huge tortoise, and that when 

 an inquiring student asked what the tortoise stood on, he was 

 severely punished for his irreverent audacity. In the case of 

 fishes we have seen that some feed on other fishes, and these on 

 lower animals", and now follows the question What do the lower 

 animals feed on ? Fishermen are apt to solve such difficulties by 

 the statement that these creatures live on suction, which is in 

 many cases perfectly true ; but what is the substance sucked in ? 

 We know that the original source of all food is the vegetable 

 kingdom, which is able to build up its substance from the air 



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