SEA-FISHERIES LABORATORY. 215 



remains of muscle fibres, and consists entirely of the 

 sarcomatous elements. 



Fig. 6, PI. II, shows very much the same condition, 

 except that in this case the muscle fibres are cut 

 longitudinally, the section is part of the edge of such a 

 massive tumour as is represented in the upper figure 

 (Text-fig. 1). It shows the hypertrophy of the con- 

 nective tissue lying between the muscle fibres. The 

 darkly-stippled part represents the fully-developed 

 sarcomatous tissue : although the morbid connective 

 tissue growth is taking place in the inter-fibrillar 

 connective tissue, the latter is not yet loaded with 

 melanin. 



Fig. 5, PI. II, represents some of the cells in a 

 fully-developed part of one of the larger tumours. The 

 structure is very obscure, but apparently consists of 

 small rounded cells, some of which stain deeply with 

 eosin and are very coarsely granular, while others are 

 loaded with melanin granules. Along with these cells 

 are masses of granules of melanin, resulting evidently 

 from the breaking down of the pigment-containing cells. 

 When treated for some days with hydrogen peroxide the 

 melanin is bleached, but the cell body then stains with 

 difficulty or not at all, and in most cases only the outer 

 cell membrane remains visible after such prolonged 

 bleaching. 



EXPLANATION OF THE PLATES. 

 Plate I. 



Fig. 1. Section through the renal organ of a mackerel 

 infected with phy corny cetous fungus. 

 Large cyst with thick fibrous wall. On the 

 left some renal tubules and lymphoid cells. 

 The longitudinal diameter of the cyst is 

 about 0'28 mm. 



