196 BULLETIN OF THE BUREAU OF FISHERIES. 



advancing disease. Subsequent examinations of the tissues showed that the probable 

 cause of this disease is a myxosporidian belonging to the genus Chloromyxum, being 

 unique in this respect. (See p. 205.) Four dead fish taken from jar no. 2 at this time 

 included two that had been introduced for the purpose of spreading the disease. After 

 seven days the fish in jar no. i were all recovering. The incised integument had closed 

 and appeared a little white. Of those in jar no. 2, two were dead, three were seriously 

 diseased and died within 24 hours, and the others had conspicuous sores. The remaining 

 14 fish from this time began to show signs of recovery, probably because they were not 

 subjected to contamination and they were fed more regularly. Twelve fish remained 

 in jar no. i and had completely recovered before the experiment was discontinued. 



In the above experiment the treatment given to the two jars was as far as possible 

 the same. Some fish escaped from both jars by jumping out. 



The first stage of this experiment, which corresponds with the first 1 1 days, was not 

 conclusive. One fish, having contracted a fatal disease from a contaminated environ- 

 ment, demonstrates the possibility that fish with apparently healthy integument may 

 acquire the ulcers. The second stage of the test, covering six days, was still less con- 

 clusive. But the third stage, covering seven days, showed beyond doubt that the infec- 

 tion enters a lesion of the integument, that contamination favors its entrance, that 

 some of these diseases may be contracted in tolerably pure water, and that lesions 

 which are not contaminated heal completely. 



Another experiment of this character was then started, making use of some of all 

 the lots of fish that had been under observation. All were in good condition. Eight 

 fish of fair size were carefully removed from this stock and, by means of a small steril- 

 ized scalpel, an incision was made back of the head and a pocket then made under the 

 integument so as to disturb the tissues as little as possible. Into this pocket was inserted 

 a bit of the diseased flesh from sores of four fish taken from different aquaria. As a 

 control, eight more fish of the same size were similarly cut, but nothing was introduced 

 into the pockets. Of the contaminated fish, four died from the disease in two days, 

 the balance in four days. In this case the disease spread over the whole upper part of 

 the body and assumed the characteristic appearance usually encountered. Only one of 

 the controls died. The others healed and recovered completely. From time to time the 

 diseased fish which were introduced into the contaminated jar and those used for the 

 inoculation experiments were examined microscopically. All were infected with bacteria. 



This last experiment, covering a period of four days, confirms the results of the 

 previous experiments as to the infectious nature of the disease as well as the inability 

 of the fish to throw off strong cultures of the causal agents. We also learn that when 

 the fish is well nourished and in a wholesome environment, it has considerable natural 

 immunity and recovers readily from the affliction. 



In order to prevent the customary mortality from this kind of affliction, care 

 should be taken not to injure the fish while collecting; no crabs or other carnivorous 

 enemies should be confined in the same tanks with the Fundulus, and after establishing 

 them in an aquarium without crowding, they should be fed on alternate days. The 

 aquarium should be kept free from dead and diseased fish. With proper circulation of 

 water, this treatment will no doubt reduce the mortality to a negligible quantity and 

 preserve the fish for several months. 



