142 GOLDFISH VARIETIES AND 
or the animals extracted from the water by a plankton net, which is 
nothing more than a small net of the finest bolting cloth. 
Besides the examination of water for living food there are many 
other interesting possibilities for the microscope in aquarium work. 
Diseases, the development of eggs, plant structure, algae, the structure 
of daphnia, cyclops and other crustacean foods are a few of the sub- 
jects which may be taken up with profitable interest. 
A study of the microscopic world within the aquarium will prove a 
most fascinating pursuit. Good microscopes for the purpose can be 
purchased very cheaply now compared with former prices. An instru- 
ment equipped with a 24 m. m. (1 inch) objective and a times 5 or 6 
eyepiece will show everything needed, giving a magnification of 60 
diameters. 
Those wishing to explore this field a little further will find the 
following works to be helpful: “Aquatic Microscopy for Beginners,” 
by Stokes; “Marvels of Pond Life,” by Slack; “Evenings at the Micro- 
scope,” by Gosse. 
