342 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
• (9) Augusts. — Twenty-two trout examined; seventeen of these with from few to 
many cysts; six of the latter with larvm escaping from cysts or under peritoneum ; one 
larva measured 54 centimeters iu length after lying for eighteen hours in water; five 
without any parasites. 
(10) August 4. — Three trout examined ; two males with few cysts, one female with 
several cysts, and one larva burrowing under the ribs. 
(11) August 6. — Four trout caught with hook, north end of lake, not far from outlet ; 
one or two cysts in each of three males; one female had a few cysts on pyloric cmca ; 
no flesh worms. 
(12) August 7. — Thirty-one trout caught with hook, north end of lake; five with 
worms in the flesh, twenty with cysts only, for the most part with only two or three; 
six without parasites. 
(13) August 9. — Nine trout caught with hook in southeast arm of lake, not far 
from inlet; one with several cysts in abdominal cavity and larvae under peritoneum. 
Six taken from near mouth of cold stream from mountain side ; four of the latter with 
cysts on i>yloric caeca, and one with a larva about 30 centimeters long in flesh near 
back-bone; five others, no flesh worms, two with cysts. 
(14) Axigust 13. — Examined a number of small trout from 12 to 20 centimeters in 
length, caught in the head waters of Alum Creek, South Fork, above hot springs. No 
cysts or other evidence of parasites discovered after very careful search. 
(15) August 25. — Examined twenty trout caught in Yellowstone Eiver near outlet 
of lake; only one was found to be much infested with parasites. It was a female and 
in lioor condition. The parasites were on and among the pyloric cseca ; no flesh worms 
noticed. On same date examined another lot of about a dozeu trout superficially. 
Only one of them was in bad condition. Upon opening it a large number of larval 
dibothria were found in the abdominal cavity. The soldiers who were fishing there 
said that they found the flsh of the river less commonly parasitized than those of the 
lake. 
(16) August 26. — At Grand Canon Hotel examined three small trout caught just 
below the upper falls. There was no indication of dibothria in these fish. A large 
front, 36 centimeters in length, also said to have been caught below the upper falls, 
was iu poor condition, and had several cysts and migrating dibothria on the pyloric 
cteca. There was, in addition, a large larva under the peritoneum and burrowing 
through the kidneys into the muscular tissue. Another specimen, said to have been 
taken above the upper falls, was also in poor condition. There were many cysts iu 
the abdominal cavity, but no larvrn iu the flesh. Another from the lake was iu good 
condition, but had several cysts on the pyloric cseca. 
In the above extracts from my notes the only parasite of which account is taken 
is Bibothrium eordiceps. As a matter of fact the trout are infested by a number of 
parasites. A small Bistomum is common in the lower intestine, and a slender, white 
nematod iu the intestine in the vicinity of the pyloric caeca. Nematods are not uncom- 
monly found encysted among the viscera, and some very peculiar soft globular cysts, 
filled with a granular fluid, looking like tumors, covered with a layer of peritoneum, 
which is richly supplied with caiiillaries, when opened liberate a small nematod. 
The latter have not yet been studied. A leruean parasite is also common, usually on 
the fins or at the base of the fins, and not rarely in the mouth. 
