Linton. — Trcmalodc Parasites of Fish 255 



the skin of fishes, but thus far the worms from these cysts 

 that have been recognized have been forms whose round of 

 life is completed in the alimentary canals of birds. As the 

 case now stands, therefore, concerning the source of the 

 trematode parasites in the flesh and skin of our fresh-water 

 fishes, that source is to be found in certain fish-eating birds. 



A SKIN PARASITE OF CERTAIN MARINE FISHES 



In a report on fish parasites collected at Woods Hole in 

 the summer of 1898, I noted the occurrence of cysts in the 

 skin of the dinner Tautogolabrus adspersus ( Bull. U. S. 

 Fish Commission, vol. xix, 1899, p. 296, pi. 40, fig. 76- 

 81). These cysts had been made the subject of a paper by 

 Ryder (Bull. U. S. Fish Commission, vol. iv, 1884, p. 37- 

 42), who attributed the cysts to cercari.'e. Later I recorded 

 similar cysts from the tautog (Tautoga onitis) (Bull. V. S. 

 Fish Commission, vol. xix, 1899, p. 463, pi. xxviii, fig. 38 ). 

 Since then I have found these cysts in the skin of a number 

 of fishes in the Woods Hole region, but in none so frequent 

 nor so abundant as in the cunner and the tautog. As it i> 

 my purpose to prepare a special report for the Bureau of 

 Fisheries on the skin parasites of fishes I shall reserve fur- 

 ther details of distribution for that paper. 



In my report on cysts from the skin of the cunner I 

 regarded these trematodes as distomes. Since that time — 

 and especially this summer — I have removed a number of 

 them from cysts, and, while I find them in agreement with 

 my published figures, I also find that I misinterpreted one 

 structure. In my figures a ventral sucker is indicated. 

 Now this structure was not clearly defined, and perhaps 

 should have been represented in a slightly different manner 

 in the diagrams. A rudiment of a sucker-like organ is 

 undoubtedly present, but instead of being a true ventral 

 sucker it more probably represents the genital aperture 

 characteristic of the family Siphoderidae (Trematodes of 

 the Dry Tortugas, Linton, 1910). 



