Il8 DOMESTICATED TROUT. 



till the ist of March. At the Cold Spring Trout 

 Ponds, they begin the same day, the 1 2th of October, 

 and finish the first week in December. 



All two-year-old trout spawn. Some yearlings do, 

 and some do not. The main dependence of the 

 trout breeder for eggs is on trout upwards of two years 

 old. The eggs of the trout are large compared with 

 those of most fish, except the salmon. They average 

 about three sixteenths of an inch in diameter, varying 

 very considerably in size, the very largest containing 

 probably twice the bulk of the very smallest. They 

 are sometimes colorless, sometimes orange-hued, and 

 sometimes have a rich red tint. 



The cause of the variation in the color of the eggs 

 is not positively known. It has been thought to be 

 hereditary. 5 * It has also been attributed to the color 

 of the flesh of its parent, and to the nature of the par- 

 ent's food.t 



A correspondent of Mr. Buckland says that the 

 tints cannot depend on the color of the parent's flesh, 

 because graylings' eggs have similar tints, and all gray- 

 lings are white-fleshed. 



The outer membrane of the egg is very elastic and 

 tough. The internal structure of the egg is as follows. 

 On the outside is the shell membrane, corresponding 

 to the hard shell of birds' eggs. Inside of this shell, 

 which is formed, as with birds' eggs, at quite a late 

 period of the development of the egg in the ovary, 

 is another membrane called the yolk membrane. This 



* Massachusetts Fisheries, Report, 1868, p. 31. 

 t Fish Hatching, Buckland, pp. 19, 20. 



