208 American Fisheries Society 



confessedly incomplete bibliography on the subject with 

 most valuable abstracts of the more general and extensive 

 articles. This bibliography covers all types of diseases, in- 

 cluding such as are of unknown origin as well as those due to 

 plant and to animal parasites. We are certainly indebted to 

 Dr. Bean for calling attention forcibly to the needs in this 

 field, and for one, I resolved at once to do what I could to- 

 ward remedying the defect in the particular line with which 

 1 was familiar. With this end in view I have brought to- 

 gether all records of parasites in North American fresh- 

 water fishes that have been published up to date, and have 

 added records of my own observations taken from field 

 notes. With these I have included records of material 

 obtained by various other investigators who have been kind 

 enough to place their collections at my disposal from time to 

 time. Some collections were not large, others were of con- 

 siderable size. All were alike valuable in furnishing evi- 

 dence as to the abundance and range of various parasites, the 

 host species infested, and seasonal or other factors that in- 

 fluence their occurrence and importance. 



Among the important fish diseases are those which 

 have been ascertained to be due to parasitic organisms. 

 These are of two types: 1. Diseases which are caused by 

 the invasion of plant parasites such as fungus, moulds, and 

 bacteria. 2. Such as are attributable to animal parasites. 

 The latter are of relatively recent discovery. In most cases 

 they are as yet imperfectlv known and their number will 

 doubtless be considerably augmented with the progress 

 of knowledge in this field. Through study diseases of un- 

 known origin are being traced to definite causes, and in the 

 majority of instances the cause is found to be a plant or 

 animal parasite. 



While the part of the lower plants in producing disease 

 has long been known, the corresponding role of animal or- 

 ganisms is a subject of relatively recent consideration. Con- 

 sequently it may be valuable to outline very briefly the recog- 

 nized ways in which animals mav be related to the cause 



