188 
LIFE, IK ITS INTERMEDIATE FORMS. 
powers to a curious purpose. It forms a residence beneath 
the surface of water, which, like our diving-bells, is filled 
with air. It is commonly said that she first spins loose 
threads, connecting the stems of water-plants, among 
which she weaves a little cell, which she then manages to 
fill with air successively carried down in bubbles from the 
surface, in some unknown manner. But Baron Walcke- 
naer, who writes from personal observation, describes the 
process differently. The abdomen is covered with a close 
down, which does not permit the water to wet the skin ; 
when beneath the surface the whole body is enveloped in 
a coat of air, so that it resembles a ball of quicksilver. 
“ When the Argyroneta would construct its nest, it 
swims to the surface, 
and, head downward, pro- 
trudes the extremity of 
the abdomen, dilating its 
spinnerets, and then 
dives with rapidity. By 
this process she produces 
a little bubble of air, 
which, independent of 
the silvery coating which 
envelopes the body, ap- 
pears as a little globule 
attached to the tail. She 
swims to the stalk of 
the plant to which she 
would fix her nest, and, The Water-Spider, 
touching it with the bubble, the air detaches itself and 
adhores to the plant. The Spider then remounts to the 
