252 American Fisheries Society 



bird, the white pelican. It is manifest that fish thus confined 

 to a lake are more exposed to infection than they would be 

 if they spent all or even a part of their time in a running- 

 stream. Furthermore, the fish in a private preserve, being in 

 large measure protected, would have a longer expectancy of 

 life than fish living under similar conditions but without 

 this protection. 



The portion of the life-history of this flesh parasite of 

 the trout which is comprised between the egg and the worm 

 as it is found in the flesh of the trout is unknown. While 

 at Alder Lake I examined a considerable number of snails 

 and found redia? in one species (Planorbis trivolvis). In 

 each of these rediae there was a large number of a very pecu- 

 liar cercaria, a description of which must be left for a more 

 technical paper than this. It is not possible at present to say 

 to what species of distome these redia? and their contained 

 cercaria^ belong. 



Certain economic questions that are suggested by this 

 flesh parasite are considered in the concluding section of 

 this paper. 



SKIN PARASITES OF FRESH-WATER FISHES 



If one will take the trouble to examine closely the skin 

 and the fins of a considerable number of fishes in certain 

 localities he will be pretty sure to find a number of small 

 spots of black pigment which, upon still closer examination, 

 will reveal a small cyst in the midst of it. When this cyst 

 is viewed with the aid of a compound microscope a young 

 trematode may be discovered folded away within its walls. 

 I have had sent to me from various localities specimens of 

 the small-mouthed black bass upon which 1 have found these 

 cvsts. Following are brief notes made on two fish sent to 

 me by Mr. C. W. Nash, of Toronto, Ontario, October 

 4, 1909: 



Each of the fish had a few black pigment spots on the 

 tins and one of them had a few also on the body, cheek's, 

 and under side of the head. Upon opening the fish along 



