REARING THE YOUNG FRY. 183 



the larger fry, it is observed, thrive better than the 

 smaller ones. 



Now the secret of getting large eggs is not to use 

 large-sized breeders, for a two-pound brook trout pro- 

 duces no larger eggs than a half-pound brook trout, 

 though they are more in number. Large eggs are the 

 result of keeping the breeders in water that warms 

 up in the spring and summer. It is true, if it becomes 

 too warm, say above 70, it is injurious; but water 

 that stands at 65 in the summer will make larger 

 eggs than water at 55, and very cold spring water, 

 say at 45, will always develop small eggs. The rea- 

 son is obvious. We know the rule is throughout the 

 animal kingdom, that warmth, when not extreme, fa- 

 vors growth, and as the temperature of the fish's 

 body corresponds to the temperature of the water,* it 

 naturally results that the eggs developed in the warmth 

 of 65 will be larger than those developed at the cold 

 point of 45. 



2. Develop strong and healthy embryos in the egg. 

 You must not suppose, when you find your trout dy- 

 ing in April and May, that the mortality is necessarily 

 caused by something that has happened since they 

 hatched. The causes may date back half-way through 

 the period of incubation or more. I have seen trout 

 embryos with the eye-spots just appearing, which I 

 knew could not live three months after coming out, 

 although they hatched like other eggs, and seemed like 



* The temperature of the fish's body follows the temperature 

 of the surrounding water, but keeps a little, perhaps two de- 

 grees, above it. 



