THE WATER SPIDER, 



241 



sloping spot with the hinge at the upper end, so that when she 

 leaves her home, or returns into her burrow, the door closes of its 

 own accord ; nay, what is still more admirable, on the interior 

 side opposite to the hinge, about thirty small holes, arranged 

 in a semicircle, may be perceived, which enable the spider to 

 hold her door down in any case of emergency against external 

 force by the insertion of her claws into some of them. The 



Water Spiders. 



outer surface of the door being on a level with the ground, 

 and covered with earth taken from the soil in which the tunnel 

 is excavated, it is evident that all traces of the burrow are lost, 

 so that a more perfect hiding-hole cannot possibly be imagined. 

 By a no less admirable instinct, the water-spider has been 

 taught to fabricate a kind of diving-bell, for which purpose she 



