SEA-FISHERIES LABORATORY. 83 



much notice of the appearance of the liver in fishes which 

 they gut, and judge of the condition of the animals by 

 the size and pigmentation of this organ. In fishes like 

 Cod and Elasniobranchs, at all events, the liver under- 

 goes seasonal changes, and a bio-chemical study of these 

 variations would be one of much interest. 



By "malignancy," then, we mean the same set of 

 anatomical conditions that are to be observed in cases of 

 human progressive growths or neoplasms, where a clinical 

 history affords data for attributing general ill-health or 

 death to the agency of the growths. Malignant tumours 

 in fishes are therefore such growths as are progressive; 

 which are not capsulated and diffuse; or which, if they 

 are capsulated show indications of breakdown of this 

 structure; and which are multiple. " Metastases " occur 

 in such cases, that is, one seldom sees a single malignant 

 tumour : usually there are many such, but whether or not 

 the metastatic growths have proceeded from a single 

 "focus" one cannot easily say. Some indications point 

 to an infective origin for these growths in fishes; and to 

 certain conditions in the environment which favour or 

 promote their occurrence, but this is a question which is 

 not easily investigated. 



All the malignant tumours which I have seen in 

 fishes are sarcomata : I have seen nothing in the least 

 resembling a carcinoma. In one or two cases details 

 of histology resembling acinose structures have been 

 observed, but these have never been so marked as to 

 justify us in speaking of the growths as other than 

 sarcomatous ones. Abnormal tissue growth, other than 

 that of the connective tissues, does not seem to occur, 

 that is, I have never seen such structures as myomata, 

 osteomata, gliomata, and the like. When a malignant 

 tumour arises in a fish it is always an overgrowth of 



