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 habits of the water-beetle — 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 ( Argyronetra aquatica). 
This Spider is a most curious and interesting creature, because 
it affords 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 
K ■ I 
