142 GOLDFISH VARIETIES A:N'D 



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. 



