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 feraz) 
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 
