ANIMAL AVOCATIONS 
231 
pond wherein they are dwelling dry up during 
the summer months. 
Even more remarkable are the habits of the 
water-spider (Argyroneta aquatica), a species 
found in ditches and ponds in the British Isles 
and other parts of Europe. It spends the 
greater part of its time under-water, even 
pursuing its prey beneath that element. When 
swimming its appearance is extremely beautiful, 
the hairs upon its body carrying and retain¬ 
ing minute bubbles of air that shine like 
silver. 
The spider spins a bell-shaped nest among 
the waterweeds for a habitation, the opening 
of the webbed structure being at the bottom. 
When this is completed, it commences to fill 
the chamber with air, frequently coming to 
the surface of the water and carrying down a 
bubble of air which is liberated beneath the 
entrance of the nest and rises to the top of the 
structure. As this work proceeds, the fairy-like 
domicile gradually gets inflated with air and 
acts as a diving-bell, so that the spider can 
dwell inside for a considerable period before 
the supply is exhausted. 
Expert divers are also to be found among 
mammals and birds ; the seal, the sea-lion and 
the walrus being the most noteworthy of the 
former, while of the latter the penguins, cor- 
