FISHES' EGGS 19 



realised how infinitesimal a percentage of eggs result in 

 adult mature roach. The same enormous destruction of 

 eggs is the rule rather than the exception throughout 

 the fish world. 



If an egg is unfertilised it soon dies, becoming white 

 and opaque. A like fate is shared by fertilised eggs when 

 under observation, if great care is not taken to keep 

 them under conditions similar to nature, as to light, 

 temperature and oxygenation. On the dead eggs of 

 freshwater fish very soon appears a fungoid growth, 

 commonly known as byssus. 



The appearance to the naked eye of an egg attacked 

 by byssus is that of a minute white woolly ball. Under 

 the microscope short shreds are seen growing out all 

 round the dead egg. The growth of byssus is very rapid. 

 In the illustration of byssus the second photograph was 

 taken only nine hours after the first. This exceptionally 

 rapid growth was due to the powerful light used, which 

 warmed up the water in the photographic cell. 



Byssus only attacks eggs and fish when dead, but 

 what is commonly known as fungus (Saprolegnia ferax) 

 attacks eggs and fish during life. 



An illustration is given showing the utter devasta- 

 tion that fungus will cause among the young trout when 

 they are attacked by it. 



Many of us who have kept gold and other fish, in 

 tanks or in small ponds in the garden, have occasionally 

 noticed white patches appear on the fins and body, and 

 have seen the fish sicken and gradually die off. These 



