i;8 THE TROUT 



This period will be longer if the water is colder, 

 and shorter if it is warmer. One degree Fahrenheit 

 makes a difference of about five days in the time. It 

 is not an advantage that the eggs should hatch out 

 quickly. Your object is to produce firm-bodied 

 healthy fry, and this is not to be done by raising the 

 temperature of the water, or by admitting strong light, 

 and so unduly hurrying the embryo through its various 

 stages of development. 



The space at my disposal does not allow me to 

 describe in detail the successive changes which, 

 during the period of incubation, go on inside the 

 transparent, horny shell of the ovum, intensely 

 interesting as these changes are to the observer. But 

 I may mention that when about a third of the 

 hatching period has passed two black spots will 

 become plainly visible in each egg. These spots are 

 destined to become the eyes of the fish, and the eggs 

 have now reached the stage at which they can, when 

 properly packed, be moved even to very long distances 

 without injury. They are known as ' eyed ova,' and 

 it is at this stage of maturity that the eggs will arrive 

 which I have advised you to purchase from a leading 

 fish-culturist. 



For packing, small shallow trays are used, made 

 of muslin, stretched on light wooden frames. These 



