48 THE AQUA VIVARIUM. 



barbuled little fish, abundant in the Thames, and a 

 very free biter, so free that he has passed into a 

 proverb ; nevertheless, he lives well in domestica- 

 tion, and not being of large size never exceeding 

 eight inches in length is well adapted for our 

 domestic experiments. 



Any of the other species of Cyprinidce which have 

 been obtained may be put into the Aquavivarium ; 

 all fish should, however, be carefully watched, lest 

 they should die. When sickening, as may easily 

 be seen by their unsteady gait when swimming, or 

 turning occasionally on to their backs, they should be 

 removed and put into fresh water, and by this means 

 they may be made to revive ; but should they die, 

 and decay in the water with other things, great 

 hazard is run of the loss of the whole of the 

 creatures. 



II. INYERTEBEATE ANIMALS. 



1. Articulata. 



The SPIDERS (Araneidce) take the highest rank 

 amongst invertebrate animals. The different groups 

 of this large family perform a surprising variety of 

 functions. They are adapted for various modes of 

 life, and one group live in the water. The habits 

 of the aquatic species differ ; some live upon the 

 surface of the water, and have their nests at the 

 edges of the pool or pond on which they live ; 

 another species has the power of diving ; it con- 

 structs its nest at the bottom of the water, and car- 

 ries down, by a peculiar arrangement, a sufficient 

 quantity of air to breathe under the water. This 

 is the common Water Spider (Argyroneta aquatica). 



