84 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



connective tissue, and it is almost always the sub- 

 integumentary connective tissues of the animal that are 

 affected. I have seen what was apparently a malignant 

 growth of the choroidal gland in a Flounder, with 

 destruction of the remaining parts of the eye ; and I have 

 also seen fibrous nodules in the liver of a Conger, probably 

 local proliferative growth of Glisson's capsule. But, in 

 general, malignant tumours in fishes are abnormal 

 developments of the sub-integumentary tissues. Not 

 enough is known as to the nature of the skin and under- 

 lying tissues in fishes to speak more definitely than this. 

 The layers beneath the epidermis differ greatly in the 

 various orders of fishes. But below the layer from which 

 the scales originate is always a layer of more or less 

 strongly developed coarse connective tissue, and this is the 

 locus of the malignant tumours of which I speak. In 

 Adami's terminology these fish growths are hylic tumours 

 of mesenchymal origin. 



The tumour, may be restricted to this situation, 

 growing as a swelling visible from without, beneath a 

 stretched or ruptured epidermis. But the tumour may 

 also be invisible from without since it may extend along 

 the connective tissue septa between the myotomes, or 

 between the smaller muscle bundles, and even between the 

 individual muscle fibres. The muscular tissue itself 

 seems never to be affected. When this growth to the 

 interior occurs, the tumours may only be recognised when 

 the flesh of the fish is cut into. 



The malignant tumour in fishes is usually a 

 melanotic sarcoma, or fibro-sarcoma, consisting of round 

 or spindle cells, or both, with a more or less abundant 

 fibrous stroma. Young tumours may be colourless, or 

 pink (apparently a stage in the formation of melanin), 

 but they are usually tinged grey or are dense black. The 



