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MAMMALS IN THE WATER 239 



take waterfowl in the reed-beds by the Nile ever swam 

 when stalking them does not appear from the ancient 

 pictures ; but the extent to which the dog voluntarily 

 becomes aquatic entitles some breeds to be considered 

 amphibious. A dog belonging to a waterman living 

 near one of the Thames ferries has been known to 

 continue swimming out in the stream for an hour 

 without coming to land. It did this for amusement on 

 a fine Sunday morning. Another riverside dog was 

 taught to dive, and fetch up stones thrown in which 

 sank to the bottom. This dog would pick out stones 

 from the bottom of a bucket of water, selecting one 

 which it had been shown before from a number of 

 others. It had so far become amphibious that it could 

 use its eyes under water. In France otter-hound 

 puppies are introduced to their aquatic life by setting 

 their kettle of soup in a pond or stream, so that they 

 must go in deep to feed. Soon they become as fast 

 swimmers on the surface as the otter itself, though the 

 physical advantages of submarine motion give the otter 

 the advantage when it is below the surface. 



As the land-rats and water-voles can swim and run 

 below water, there is no reason to suppose that the 

 various tribes of mice cannot do the same. The house- 

 mouse swims on the surface as well as the rat, but it 

 has, apparently, not yet learnt to dive. All the pachy- 

 derms can swim, and very many are as much at home 



