EXPLORATIONS IN YELLOWSTONE NATIONAL PARK. 
51 
aininecl by us from the Yellowstone, between the falls and the Lake, all showed some 
traces of the presence of the worm. These were first noticed by us as small whitish 
cysts, about as large as a grain of wheat, around the pyloric coeca, sometimes in the 
ovary. These cysts contain small worms, apparently similar to the larger ones. These 
larger worms, from 1 to 5 inches in length, are found in the liver, in the abdominal 
cavity, or in the muscular substance of the belly or sides. When worms exist in the 
flesh they can usually be found by skinning, as the flesh about them is more or less 
diseased. These facts may perhaps be better appreciated by the following notes on 
specimens examined : 
Female (dissectert) from Yellowstone River (taken like the next four in the eddy at the bend of the 
river, about miles above the Giant’s Cauldron and Mud Geyser). A worm 10 inches in length, in 
a sac along the -intestine ; another worm about 4 inches long, in a sack, in the muscle of the ab- 
dominal wall, the flesh pale and diseased for an inch about the worm. Ovaries full of little worm 
cysts, and imperfectly developed. Numerous cysts among the pyloric coeca in this and all other- 
diseased specimens. 
A large male (No. 137) : Liver, iryloric coeca, and spleen with worms ; the worm in liver large. Testes 
wholly empty and shrunken. Had external appearance of a female trout. 
Male (421) : No worms evident, except a few cysts about the stomach ; testes full and normal. 
Female; No worms evident; ovaries large and full of normal eggs; cysts present among the pyloric 
coeca in this and all other specimens from Yellowstone River. 
Male (28.')); Pyloric coeca full of cysts. 
Males (323, 244) ; Worms present ; sexual organs little developed. 
Nos. 3 and 4, Riddle Lake. Viscera normal ; no trace of worms or cysts. 
Female (494) ; from Heart Lake, at mouth of Witch Creek ; intestines and cmca with cysts and with 
some small worms. Other worm-like parasites of other genera in cavity of mouth and on dorsal 
fin. 
Young male (365); Heart Lake: a single small encysted worm among the pyloric coeca ; no others 
evident. 
A basket of dressed trout, taken in the Yellowstone Elver at Livingston was ex- 
amined. Among these was one worm 3 inches long, apparently of the same species 
as the others. Numerous other specimens were examined without developing any 
facts other than those included below. 
I offer the following generalizations with much hesitation, as I know practically 
nothing of the life-history of intestinal worms of the group to which Dibothrium 
belongs. 
Worms are found more or less abundant in nine-tenths or more of the grown trout 
in the Yellowstone Lake, and its larger tributaries, and in the Yellowstone Eiver as 
far as the Lower or Great Falls. The trout in the upper Yellowstone are likewise 
affected, those in Bridgets Lake being (according to Mr. A.rnold Hague) largely 
w'ormy, as also those in Atlantic Creek (Elwood Hofer). The small trout (under 6 
inches) have not been found to contain worms. 
Worms are popularly believed not to exist in the Lower Yellowstone (below the 
falls). The discovery of a worm at Livingston would contradict this. Perhaps worms 
exist, but are small or scarce. Those in the encysted condition would hardly attract 
popular notice, for ordinary observers do not even distinguish the worms from the 
pyloric coeca. 
Worms certainly exist in the trout of Heart Lake, to all appearance identical spe- 
cifically with those in Yellowstone Lake. This lake is on the west side of the Divide 
and is drained by Snake Eiver. It has at present no connection with Yellowstone 
Lake. 
