TROUT BREEDING. 137 



tliey will be secure from all those circumstances which might 

 injure them. They must at once be supplied, if they are trout 

 eggs, with a stream of water which will be constantly renewed, 

 and constantly maintain a low temperature. And you must, if 

 possible, avoid one great source of loss among these eggs, 

 which is found in a minute little plant, known as water-silk, 

 which consists of threadlike growth, of about the thickness of 

 the finest silk thread, of a greenish color, and which multiplies 

 very rapidly in some waters. In localities where that vegetation 

 is abundant, there is little chance of being successful, because 

 the seeds of the water-silk, which are exceedingly minute, float- 

 ing in the water, will adhere to the eggs, root in them, and very 

 soon kill the germ of the fish. There is only one way to obvi- 

 ate this difficulty, where it is in a measure inevitable. It is to 

 place the eggs in such a position that the water which flows 

 upon them will keep them revolving, and not allow them to re- 

 main stationary upon the bottom. That is one very important 

 point — to have the water flowing over the eggs in such a man- 

 ner that they are more or less kept in motion. The flow of 

 water should be sufficiently strong to disturb the eggs from their 

 position, and make them rise and fall. If they are raised too 

 much, they may be carried along ; but if they are only raised 

 slightly, they will then just be in a position to avoid the deposit 

 of the seeds of this vegetation upon them, which destroys them 

 so rapidly. 



The covering of the eggs with the milt is of course an indis- 

 pensable condition for the fecundation of the eggs, and when 

 they have once been fecundated, the process of growing goes on 

 gradually and steadily. At that time, the eggs are perfectly 

 transparent. The moment you see an egg turn opaque, you 

 may be sure it is dead, and the sooner you remove it the better, 

 for it will decay and become the cause of infection, and there- 

 fore ought to be removed. As long as the egg is alive, it re- 

 mains transparent. Even after the young fish is formed, and 

 when it has reached a considerable stage of progress, it is still 

 transparent, or it has such a lively color that it shows by its 

 very tint that it is alive. 



[The Professor proceeded to show, by the use of the black- 

 board, the process of the formation of the fish in the egg, repre- 

 senting its appearance in the various stages of development. 



18 



