SEA-FISHERIES LABORATORY. 303 



the fish was also examined, but was quite normal. Indeed, 

 with the exception of the tumour described no other 

 evidence of disease could be discovered. 



The tissue of the tumour showed a general resem- 

 blance to that described in the case of the young salmon. 

 But there was a much larger quantity of broken down 

 material, of a finely granular nature, lying between the 

 cells. The latter are apparently epidermal cells altered 

 considerably, staining only very lightly with 

 Romano wsky, but deeply with iron-alum haematoxylin. 

 Among these cells are nests of bacteria staining well with 

 Romanowsky. Several of these are represented in fig. 3, 

 pi. VIII, and it will be seen that they are of very various 

 forms. The long delicate bacillus occurs rather rarely; 

 it is about 10 /x in length. Other forms are short curved 

 rods and thick, dumpy bacilli, most of which stain as if 

 spore formation were in progress, but are probably only 

 the involution forms of a bacillus akin to the long slender 

 forms. These bacilli are not very numerous, though a fair 

 number could be seen in every field. An attempt was 

 made from the fresh tissue to set up a cultivation on 

 nutrient gelatine at ordinary room temperature, but no 

 results were obtained. Probably they represent only a 

 secondary infection on a partially broken down prolifera- 

 tion of the epidermis. The whole appearance of the latter 

 is so similar to that in the Manx salmon parr that I am 

 inclined to regard this also as a case of dermal catarrh. 

 A mechanical injury is out of the question as the skin 

 underneath was almost normal and no traces of infection 

 by a sporozoan or other parasite could be detected. 



