20 American Fisheries Society 



brought against the butterfish, viz., that large numbers 

 of them had nematode worms in the flesh. 



Now, as it happens, I had examined large numbers of 

 butterfish for flesh parasites in the past ten years and, 

 having found their flesh free from nematode parasites I 

 was not at all disposed to believe that butterfish had 

 suddenly become parasitized in this way. I was familiar 

 with the fact that nematodes are of common occurrence 

 on the viscera, especially on the pyloric caeca, of the but- 

 terfish, an affiliction shared with the butterfish by many 

 other species of fish to a greater or less degree, and sug- 

 gested that nematodes seen on the viscera had been mis- 

 takenly referred to the muscle tissue. This created an 

 issue, an impasse in truth, which could be resolved only 

 by an investigation to see how the facts lay. Accord- 

 ingly some butterfish were sent for and brought from 

 the market. A fish was opened. Nematodes were found 

 on the viscera, but none in the flesh except a few that had 

 been carried thither by the knife used in opening the 

 fish. The remaining fish were opened more carefully 

 with the result that nematodes, so far as they were pres- 

 ent at all, were found only on the viscera. 



Detailed results of the examination of butterfish for 

 nematode parasites are given below. 



Before taking up the discussion of the particular case 

 afforded by the butterfish I shall discuss briefly the gen- 

 eral question of the effect on food values of the presence 

 of representatives of different orders of helminths in 

 food fishes. Preliminary to this, however, I shall ask 

 indulgence for a few remarks on the general subject of 

 parasites. The late Joseph Leidy, many years ago, made 

 an interesting contribution to science in a paper entitled 

 A Fauna and Flora within Animals. The title alone was 

 a valuable gift to popular knowledge. That paper 

 showed that there exist in nature large numbers of 

 species of animals and plants which pass all, or an im- 

 portant part, of their existence within the bodies of 

 animals. The indweller is called a parasite or guest ; the 

 animal which harbors the indweller is called the host. 



