American Fisheries Society. 81 



you are as l^adly off with cement ponds as you are with wooden 

 ponds, but happily this original infection will probably be com- 

 paratively rare. 



Mr. Sykes: Where diseased fish are put into another pond 

 they must leave the germs of the disease in that pond. 



Prof. Marsh : Yes, sir. 



Mr. Sykes : You put diseased fish into earth ponds ? 



Prof. Marsh : Yes. 



Mr. Sykes : Your idea is that the soil becomes polluted with 

 this disease germ, yet in the nature of things that must leave 

 the new pond in the same condition. 



Prof. Marsh : It has not done so yet, because it has not had 

 time. The large earth pond would be infected more slowly be- 

 cause of its size. 



Mr. Sykes: Your idea is that these disease germs multiply 

 in the soil and do not tend to die out ? 



Prof. Marsh : In a plain earth pond or wooden pond the 

 tendency is for them to grow. The water soaks in through the 

 boards and there is nothing but a wet mush full of organic ma- 

 terial, and they will grow in that, but in a natural pond of vege- 

 tation I think there is less chance for it, because it is not quite so 

 rotten down there. 



Mr. Sykes : You make a distinction between an earth pond 

 with vegetation and a board pond without vegetation ? 



Prof. ]\Iarsh : \ es. 



