TREMATODES FROM FISHES — LINTON 161 



of pharynx, 0.04 mm., of ventral sucker, 0.04 mm. ; middle and ante- 

 rior regions with numerous subspherical bodies from 0.007 to 0.010 

 mm. in diameter. Measurements in balsam: Length, 0.90 mm. (fore 

 and hind body about equal) ; maximum breadth, 0.30 mm. ; breadth 

 of oral sucker, about 0.07 mm., of pharynx (indistinct) about 0.024, 

 of ventral sucker, 0.036 mm. In another balsam specimen: Breadth 

 of oral sucker, 0.054 mm., of ventral sucker, 0.033 mm.; hold-fast 

 organ, length, 0.069 mm., breadth, 0.048 mm. 



On July 3 and 4, 1904, a number of brook trout, 60 more or less, 

 were examined for skin parasites, at Alder Lake in the Catskills, 

 near Turnwood, N. Y. Many of them had cysts surrounded by 

 black pigment on the skin. None of the fish had large numbers of 

 cysts. A feAv had as many as from 25 to 30 cysts on each side. 

 Some had from one to five cysts on a side; others were free from 

 cysts. The cysts lie just beneath the epidermis so that a consid- 

 erable number of them produce an embossed surface which can be 

 detected by passing the hand lightly over it. Many of these cysts 

 were opened and found to contain larval trematodes, all apparently 

 of the same species. The cysts were from 0.4 to 0.7 mm. in diameter. 

 One cyst 0.56 mm. in diameter had walls 0.15 mm. thick. The 

 liberated larva was 0.22 mm. in length and 0.14 mm. in breadth. 

 A larva removed from its cyst and flattened under the cover glass 

 had the following measurements: Length, 0.28 mm.; diameter of 

 oral sucker, 0.044 mm., of pharynx, 0.020 mm., of ventral sucker, 

 0.054 mm. A transverse slit with deeply staining walls, marking 

 the position of the hold-fast organ, is a conspicuous feature. A re- 

 port of this investigation Vv^as published in "The diagnosis of a case 

 of parasitism in the brook trout," Proc. Int. Zool. Cong., 1907, pp. 

 629, 632. 



On May 25, 1908, I received from Dr. Tarleton H. Bean three 

 yellow perch (U.S.N.M. No. 8399) which had been taken in Amper- 

 sand Pond, in the Adirondacks, by J. C. Hanchett, Superintendent 

 of Knollwood Club. The fishes were thickly covered with en- 

 cj'sted trematodes, surrounded by black pigment, similar in appear- 

 ance to those of the brook trout. The cysts were distributed indis- 

 criminately over the body, on the fins and eyes, each containing an 

 immature trematode larva. 



Seven yellow perch were seined in a fresh-water pond at Quisset, 

 near Woods Hole, on July 1, 1913, A few trematode cysts in the skin, 

 beneath the scales. Cyst, 0.48 by 0.40 mm.; larva liberated from 

 the cyst, but still enveloped in a thin membrane, 0.30 by 0.20 mm. 

 Another cyst, 0.49 mm. in diameter, contained a larval trematode, 

 length, 0.25 mm., breadth, 0.17 mm. 



155599—40 11 



