SEA-FISHERIES LABORATORY. 87 



section) shows several growths which are apparently 

 independent of each other, that is, each is surrounded by 

 a distinct thin capsule. In hand sections of the fresh 

 material these tumours show as either creamy white or 

 grey in colour, with black mottling due to melanin 

 impregnation. Text-fig. 2, which is part of a transverse 

 section through the fish, shows two small rounded tumours 

 containing some melanin, and also several larger ones 

 which are nearly colourless. These figures represent 

 fairly well the appearances disclosed by making hand 

 sections, in various planes, through the flesh of the fish 

 behind the anus. Almost everywhere there were rounded 

 tumours which were usually to be recognised by their pink 

 or grey or black colour, but which were sometimes 

 colourless and recognisable only by their texture. 

 Usually they could be seen to possess definite boundaries, 

 that is, distinct thin capsules. They were generally 

 situated immediately beneath the skin, but sometimes 

 they were apparently embedded in the muscles. Some 

 were surrounded by adipose tissue. In the Halibut, 

 unlike most Pleuronectid fishes, there is, in large, well- 

 fed fishes, a rather thick layer of fat near the bases of 

 dorsal and ventral fins, on either side of the axonosts. 

 Sometimes there were small tumours in the middle of this 

 fatty tissue. 



Encapsulation and Boundaries of the Tumours. 



Hand sections made through the flesh of the fish by 

 means of a sharp razor showed that the tumours 

 were usually definitely bounded. This definite outline 

 suggested the presence of a capsular structure, but when 

 microtome sections were made, stained and mounted, it 

 was seen that such a capsule was not always present, and 

 when it was present there were often indications of its 



