276 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
From the pylorus was obtained a single specimen of Tetrarhynchus robustus (Cestode Parasites of 
Fishes) p. 452. 
One of the larger specimens of R. agile measured 95 mm. in length. It was noticed that these 
specimens contracted very greatly when placed in the killing fluid (Long’s aceto-picro-mercuric 
fluid), especially the mature and maturing proglottides, some of the latter contracting to one-fourth 
their length. Specimens were then stretched on the bottom of a glass dish and allowed to lie there a 
short time until they were fastened by their own mucilage. They did not then contract when the 
killing fluid was placed on them. 
11a. Catostomus commersonii, Common Sucker. 
August 26, I received a specimen of sucker and a bottle containing a large number of parasitic 
copepods, which were sent to me by Dr. H. M. Smith. Along with the specimens was a letter from J. W. 
Titcomb, superintendent of the Fish Commission station at St. Johnsbury, Yt. The fish and par- 
asites had been collected by I. W. Parks, Montpelier, Yt. Mr. Titcomb wrote: 
Through the courtesy of I. W. Parks, veterinary surgeon at Montpelier, 4 r t., I have obtained a 
lot of specimens of the parasite which infested the river there this summer and a sucker which had 
been attacked by them. It will be noticed that one of the pectoral tins is quite badly eaten aud a 
spot on the flsh below it. These parasites usually attack the pectoral tins tirst. They are sometimes 
found on the eyes of the flsh and apparently stand on their heads in working into the fish. 
These parasites belong to the genus Argulus, probably A. catostomi Dana and Herrick. The 
abraded place on the side of the flsh was examined and the tissues were found to be penetrated by the 
hyphse of some fungus, presumably a species of Saprolegnia. Since the mouth parts of Argulus are 
fitted for piercing and sucking, and not for biting, it seems rather hard to account for the frayed and 
tattered condition of one of the pectoral fins of this fish. Because of the presence of the fungus noted 
above, I stated in my letter to Dr. Smith relative to this case that these parasites may not have been 
wholly to blame for the damage, although the trouble might have been started by them. 
Later I received a letter from Mr. Parks, dated September 20, in which he gives an interesting 
account of his observations on the effect of these parasites on trout aud suckers. The following 
extracts, give the substance of his observations. After speaking of a fish which had no marks of any 
kind upon it when he first saw it, which was swimming in shallow and clear water, he proceeds: 
First the fish swam along in the usual manner feeding, but soon became uneasy, this increasing 
until it seemed to become frenzied. This stage does not last more than 30 minutes, however — and 
then it commenced to turn upon its back and became comatose and soon died. * * * To make 
sure the parasite was the cause of death I obtained trout and suckers from an adjacent stream, and 
after placing the sucker in a tank of fresh water I dropped in about fifty of the parasites, which at 
once attacked the fish. While they were upon the sucker I placed three trout in also. In 55 minutes 
I noticed signs of frenzy and in 75 minutes coma, and in 90 minutes the first trout was dead, and upon 
examination I found the left pectoral fin completely stripped, the right eye destroyed, a spot near the 
tail stripped of the scales the size of a ten-cent piece. 1 find that suckers can live longer than trout, 
also the parasites will go from a sucker to trout. 
The Argulidce, according to Claus (Zeitschrift fur Wissenschaft, Zool., xxv, 3, 1875, p. 277), live 
on very different sorts of fish, and chiefly on the plasma of the blood to which they obtain access by 
means of modified mandibles and maxillm which are transformed into a piercing and sucking organ. 
12. Anguilla chrysypa, Common Eel. 
(1) July 25; one; stomach empty. 
Cestodes: Cysts containing larvse, on mesentery, several, Rhynchobotlirium imparispine Lt. (Ces- 
tode Parasites of Fishes, p. 450.) 
Nematodes; one encapsuled on liver, immature; not yet identified. There was an inflamed patch 
on the stomach wall and on the intestine, evidently caused by a wound on the side. 
(2) August 5; one; partly digested fish in stomach. 
One hyaline cyst on viscera, containing a Ehynchobothrium larva. When released it remained 
attached to the blastocyst. 
(3) August 29; one; stomach empty. 
The only entozoon found was a single immature cestode larva of the type which I have found 
in the alimentary canals of a variety of fish; small, with two red spots on the neck. (Larval Cestode 
Parasites of Fishes, pp. 789-792, pi. lxj, figs. 4-15.) The stomach and intestine were washed and the 
contents looked over very carefulty with the above meager result. The specimen had been in an 
aquarium for a few days. 
