258 American Fisheries Society 



loon, the chances that they would develop in so widely dif- 

 ferent a host as man are very remote indeed. 



With respect to the skin parasites it will readily be seen 

 that most of them are removed in the preparation of the 

 fish for the table, so that the chances of any of them enter- 

 ing our food are not great. It may be a quieting thought 

 also to remind those interested that the flesh parasites would 

 hardly escape the notice of a careful cook. To all this it 

 may be added that since we in this country prefer to have 

 fish well cooked when it is served as food, the danger of 

 infection from this source is reduced to a minimum even if 

 the parasites were capable of continuing their development 

 in a mammal host, and that mammal the genus man. 



Nevertheless if the parasites are not injurious to man in 

 a pathological way their presence in our food is still most 

 objectionable. Indeed their presence in any considerable 

 numbers in an occasional fish, or in any considerable pro- 

 portion of fish, aside from the direct injury which they may 

 inflict on the fish, will, of course, render them undesirable 

 if not actually unfit for food. 



It should be borne in mind that neither the flesh para- 

 site nor the skin parasite can multiply in its encysted state. 

 Their only chance of attaining the adult egg-producing stage 

 of existence is that they with their host be eaten by the par- 

 ticular kind of animal to whose alimentary canal they are by 

 long adaptation and selection suited. Their prayer is for a 

 suitable and timely devourer. 



Since the original source of infection for both the flesh 

 parasites and the skin parasites that are made the subjects 

 of inquiry in this paper is found in a fish-eating bird, the 

 control of both can be considered as one question. 



Where fish are confined to ponds or small lakes the 

 question resolves itself into the practical one of excluding 

 fish-eating birds from small bodies of water. While such 

 exclusion may not always be practicable, the infection of the 

 waters may be in great measure prevented by vigilance in 

 shooting objectionable bird visitors. 



