THE MICROSCOPICAL AQUARIUM. 



35 



pond be accessible, three parts of the tank are filled with 

 water from it ; if it be cloudy or even muddy, the result 

 may be more favourable. After being left in repose for 

 at least a week, the character of the contents (if the pond 

 be fairly productive) will be seen ; the water will be clear 

 and probably reveal a variety of common objects, such as 

 larva of insects, entomostraca, planaria, and hydrae ; in a 

 week or more vegetable growth will appear, covering 

 every portion of the interior. The tank is now in a con- 

 dition to be inoculated with whatever choice objects can 

 be obtained, the result of special and favourable gather- 

 ings, and this should be repeated frequently ; the front 

 glass must be occasionally cleaned with a sponge tied to 

 the end of a cane, but on no account be tempted to touch 

 the sides or back : the water will soon become as clear 

 as crystal, however muddy it may have been when first 

 introduced. The pieces of stone will show signs of vege- 

 table growth, with patches of such forms of infusoria as 

 vorticella and stentors. The waste from evaporation 

 must be supplied by additions of pond water (the richer 

 the better), and such a tank will be, in a month or two, 

 (not before), a marvel of microscopic beauty and interest. 

 The untouched back glass will be covered with a dense 

 mantle of dark-green velvety vegetation, in the midst of 

 which will be discovered groups and patches of the fixed 

 infusoria, and it is essentially the habitat of the polyzoa ; 

 hydrae, and the rarer rotifer philodina, even melicerta, 

 and stephanoceros, may be found under such circum- 

 stances, to say nothing of the countless tribes of free 

 infusoria, ever ready for observation in all their various 

 phases of existence, and such conditions will preserve 

 and increase them indefinitely. Enemies to eliminate 

 are larvae of insects (but these soon disappear naturally), 



