90 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



is here a mixed-cell sarcoma. Round most of this nodule 

 is a thin fibrous capsule similar to those represented in 

 fig. 1, but at the place shown in fig. 3 this has quite 

 broken down. There is no indication here of connective 

 tissue fibres, except the arrangement of the elongated 

 nuclei. Round the nodule are ordinary striped muscle 

 fibres, and these have quite broken down at one place, and 

 the sarcoma is actively growing here and is invading the 

 interspaces between the muscle fibres, spreading along 

 the connective tissue stroma among the latter. This 

 seems to be quite typical of the manner in which these fish 

 sarcomata proliferate. Fig. 1 of Plate III represents a 

 small part of the same field drawn in fig. 3 of Plate II, 

 but seen under an apochromatic lens, and greatly 

 magnified. On the lower margin of the figure are parts of 

 two unchanged striped muscle fibres, while the rest of the 

 figure represents the changes undergone by other similar 

 fibres as the result of the proximity of the sarcoma. 

 What we have here is apparently a condition resembling 

 the Zenker ian degeneration of striped muscle fibres 

 induced as the result of various causes : it is a special 

 kind of necrotic change. The sarcolemma appears to 

 remain intact, but the striation of the fibre quite 

 disappears, and its substance seems to become replaced by 

 some hyaline, non-staining, waxy material. But here 

 also we have a multiplication of the nuclei of the fibre, or 

 perhaps the invasion of the latter by extraneous cells. 

 The space within the sarcolemma is filled by large 

 numbers of small oval cells. These may have resulted 

 from the multiplication of the original muscle nuclei, but 

 they may also have migrated in the individual fibres from 

 without. It is doubtful whether much of the tissue of 

 the sarcomatous nodule has originated in this way : it is 

 more likely that this replacement of the muscle fibres by 



