2 28 TWELFTH ANNUAL REPORT OF THE 



disease in the Baltic and in Italian waters is very probable because of the 

 identical symptoms and the similar course of the disease. More thorough 

 investigations on these points are, nevertheless, much desired. 



As to the origin of the Red Plague nothing satisfactory has been made 

 known for a long time. It is believed that in the Baltic the high tempera- 

 ture of the summer is very favorable to the spread of the disease and to 

 the great mortality. Sennebogen makes the same statement in Italy. 



For the prevention of the Red Plague, at least in ponds, their estab- 

 lishment, according to Canestrini, may be recommended in fresh water, 

 in which the Bacillus anguillarum is said to develop very scantily. Senne- 

 bogen, on the other hand, disputes positively the checking action of fresh 

 water, because he has seen the Red Plague reproduce itself even in pure 

 fresh water. 



Fungus. 



It is uncertain whether or not fungus is a primary cause of fish disease, 

 but it is a very disagreeable and injurious associate of certain diseases. 

 At one station a kind of fungus appeared on the back fin, the body behind 

 the back fin, and on the tail. When attacked, the affected regions turned 

 white, and the fish died very quickly. The remedies applied were a plenti- 

 ful flow of cold water, thinning out, and the free use of salt. 



Copper Sulphate. 



The excessive growth of certain water plants in ponds and streams 

 devoted to fish breeding is sometimes a source of trouble and loss. In 

 order to control this difficulty, blue vitriol has been used as an algicide, 

 and sometimes the results have been satisfactory. Experiments with the 

 vitriol have been conducted by the U. S. Bureau of Fisheries and the U. S. 

 Department of Agriculture. 



A practical problem arising in the use of such an irritant caustic is 

 to ascertain the strength of a solution which will destroy the alga; and not 

 injure the fish or fish food. Useful articles in this connection are those of 

 Mr. M. C. Marsh, published in the Bulletin of the Fisheries Bureau, and in 

 the Transactions of the American Fisheries Society for 1905, and Bulletins 



