1614 THE STORY OF THE UNIVERSE 



and reconnoitres. If a small creature is seen, it 

 is seized and devoured. If the invader is more 

 formidable, the door is quickly closed, seized and 

 held down by the spider, so that much force is 

 required to lever it open. Then, with the intruder 

 looking down upon him, the spider drops to the 

 bottom of his shaft. 



It has been found by many experiments that when 

 the door of his nest is removed, the spider can renew 

 it five times never more than that. Within these 

 limitations, the door torn off in the evening was 

 found replaced by a new one in the morning. Each 

 successive renewal showed, however, a greater pro- 

 portion of earth, and a smaller proportion of silk, 

 until finally the fifth door had barely enough silk to 

 hold the earth together. The sixth attempt, if made, 

 was a failure, because the spinnerets had exhausted 

 their supply of the web fluid. When the poor per- 

 secuted spider finds his domicile thus open and de- 

 fenceless, he is compelled to leave it, and wait until 

 his stock of web fluid is renewed. 



Skilful diggers prepare burrows with several en- 

 trances ; some even arrange several rooms, each for a 

 special object. The otter seeks its food in the water, 

 and actively hunts fish in ponds and rivers. But 

 when fishing is over, it likes to keep dry and at the 

 same time sheltered from terrestrial enemies. Its 

 dwelling must also present an easy opening into the 

 water. In order to fulfil all the conditions, its house 

 consists first of a large room hollowed in the bank at 

 a level sufficiently high to be beyond reach of floods. 

 From the bottom of this keep a passage starts which 



