THE WATER SPIDER. 



229 



look into the water. True, I might have fallen into the river, 

 but I never did ; and even had that accident occurred, it would 

 have wrought no harm, except wet clothes, for I could swim 

 nearly as well as the water-insects themselves. . 



Close under the bank lived some creatures which always 

 interested me greatly. Spiders they certainly were, but they 

 appeared to have the liabits of the water-beede — coming slowly 

 to the surface of the water, giving a kind of flirt in the air, and 

 then disappearing into the depths, looking like balls of shining 

 silver as they sank down. I had been familiar with these 

 creatures for years before I met with them in some book, and 

 learned that they were known under the name of Water 

 Spider {Argyronctra aqnatica). 



This Spider is a most curious and interesting creature, because 

 it aftbrds an example of an animal which breathes atmospheric 

 air constructing a home beneath the water, and filling it with 

 the air needful for respiration. 



The sub-aquatic cell of the Water Spider may be found in 

 many rivers and ditches, where the water does not run very 

 swiftly. It is made of silk, as is the case with all spiders' nests, 

 and is generally egg-shaped, having an opening below. This 

 cell is filled with air ; and if the Spider be kept in a glass vessel, 

 it may be seen reposing in the cell, with its head downwards, 

 after the manner of its tribe. The precise analogy between 

 this nest and the diving-bell of the present day is too obvious 

 to need a detailed account. How the air is introduced into the 

 cell is a problem that was for some time unsolved. The reader 

 is probably aware that the bubbles of air which are to be seen 

 on sub-aquatic plants are almost entirely composed of oxygen 

 gas, which is exuded from the plant, and which is so important 

 an agent in purifying the water. Some zoologists thought that 

 the air which is found in the cell of the Water Spider was 

 nothing but oxygen that had been exuded from the plant upon 

 which the nest was fixed, and that it had been intercepted in 

 its passage to the surface. In order to set the question at rest, 

 Mr. Bell, the well-known naturalist, instituted a series of ex- 

 periments upon the Spider, and communicated the results to the 



