60 
Diseases of Fisli 
were visible, and it was possible to trace the gradual disappearance of 
the muscular striae, until the whole muscle fibre had become changed to 
a structureless mass. The sarcolemma persists to a comparatively late 
stage, and then apparently vanishes, when the individual fibres fuse 
together into a structureless homogeneous mass. In places, the muscular 
fibres which had commenced to degenerate, were invaded by leucocytes 
(fig. 5), and in some cases the fibres were replaced by a mass of leucocytes 
and fibrin, though the sarcolemma was partially persistent A marked 
overgrowth of fibrous tissue between the fibres was commonly found. 
This appears to be a remarkably advanced case of the ‘ dd- 
generescence vitreuse,’ described by Thelohan (9) as occurring in the 
muscles of Callionymus lyra when infected by Glugea destruans. 
Unfortunately it was impossible to identify the sporozoon to which the 
degeneration was due, as only a few imperfectly preserved spores were 
present in the tissues, but from their shape and size, and the analogy of 
their effect on the host with that of Glugea destruans, it would appear 
probable that this is also a case of an infection by a species of Glugea. 
A case of Epithelioma papulosum in Pleuronectes platessa. 
This specimen (fig. 7) was a female, measuring 28 centimetres in 
length. The fish showed a number of circular, white, papillary 
elevations, some measuring as much as 14 mm. in diameter, irregularly 
distributed over the ocular surface. 
Sections (fig. 6) cut at right angles to the surface of the skin, showed 
that the elevations consisted entirely of epidermal cells, superimposed 
so as to form a thick mass : they gradually thinned away at the periphery 
and became directly continuous with the normal epidermis. There was 
no invasion of the deeper tissues. 
The condition appeal's to be similar to that found in the Carp 
disease (Pochenkrankheit) described by Hofer (6), and Doflein (2 and 3), 
who found that though the lesions of the skin were free from any parasitic 
infection, yet the kidney and sometimes the liver and testis or ovary, 
were infected with a Myxoholus, to which they gave the name of the 
Myxoholus cyprini. According to them, the skin lesions are an entirely 
secondary result, due to the formation of toxins by the organs infected 
with the sporozoon. On the other hand, Fiebiger (4) has found that 
apparently perfectly normal Carp are sometimes infected with the 
Myxoholus cyprini, and also has often been unable to detect the 
Myxoholus in fish obviously affected with Epithelioma papulosum. 
