248 American Fisheries Society 



cercarise are without tails, thus indicating that they pass to 

 the final host directly when the intermediate host in which 

 they are lodged is swallowed by the proper animal. From 

 25 to 50 or more cercariae may be counted in sporocysts 

 which I have collected from molluscs and an annelid worm 

 at Woods Hole. If rediae are produced in like numbers in 

 cases where that stage appears, then the number of cerca- 

 riae which may arise from a single egg might be the last 

 term in a geometrical progression in which the first term is 

 one, the number of terms at least three, and the ratio as 

 much as 50, or even more. This would be interpreted as 1 

 egg, ciliated larva and sporocyst, 50 redise, and 2,500 cerca- 

 rise. In cases where another generation of sporocysts or of 

 redise appears, another term, or perhaps two would be added 

 to the progression. 



A FLESH PARASITE OF THE BLACK BASS AND OTHER FRESH- 

 WATER FISHES 



In a recent contribution to the Biological Bulletin (vol. 

 xx, p. 350-366), Prof. H. L. Osborn has brought together 

 the literature on an interesting distome of wide distribution. 

 It has been recorded under a variety of names by different 

 observers but the name which seems to have priority is 

 Clinostomum marginatum. This distome has been described 

 and recorded by several observers from a variety of hosts. 

 In the larval or encysted stage it has been reported from the 

 yellow perch, striped bass, two species of sunfish, the small- 

 mouthed black bass, a silurid fish, and at least one species 

 of frog. The localities from which it has been reported are 

 Kansas City, Mo.; Montreal, Ontario; Nebish, Mich.; Phila- 

 delphia, Pa.; Porto Rico; St. Paul, Minn.; Toronto, On- 

 tario; Troy, N. Y. In most cases the seat of infection is in 

 the muscles, but it was also found in the gills, the branchi- 

 ostegal membranes, the fins, and the mouth. More than 

 ordinary interest attaches to this worm from the fact that we 

 have here a parasite which infests portions of the fish that 

 are used as food. Osborn reports that at Nebish, Mich., in 



