SWIMMING ANIMALS 83 



cold northern waters to reach the immense size of seven and 

 a half feet across, with tentacles 120 feet in length. These 

 tentacles are armed with batteries of stinging cells. Undei 

 the shelter of these jellyfish the small whiting find a 

 temporary home. On a calm day it is at times possible to 

 see one of these jellyfish floating near the surface of the 

 water, and all around within a radius of a few feet can be 

 seen numbers of these little whiting darting about picking 

 up their food. A sudden splash with the oar will drive them 

 all beneath their curious shelter where they rest secure, 

 trusting in the stinging powers of their host as a protection 

 against their enemies. And the amazing thing is that the 

 jellyfish allows it and does not attempt to capture them. 

 In European waters the baby horse-mackerel {Caranx 

 trachurus) also seek this floating shelter, while in American 

 waters young butterfish {Poronotus triacanthus) do likewise, 

 as well as young haddock and cod from both sides of the 

 Atlantic. 



All our tiat-fishes, such as plaice and soles, spend the first 

 days of their lives drifting freely through the water. But 

 at this period they are rather unlike their parents. The full- 

 grown fishes, as we all know, have both eyes on the same side 

 of the head ; but not so the very young fishes, which are 

 quite symmetrical, with one eye correctly placed on each 

 side of the head. After two or three weeks, however, the 

 eye on one side begins to move and slowly travels over the 

 top of the head until it reaches the other side. At this 

 stage the fish turns over on its side and seeks the bottom 

 where it lies, with eyes both pointing upwards. This 

 shows that many of the flat-fishes are flattened sideways, 

 and are, indeed, living on the bottom on their sides. Such 

 fishes are the plaice, the sole, the brill, the turbot and 

 many others. Some fishes, however, such as the skate 

 and the Angler Fish, may be flattened from above downwards, 



G 



