ZOOLOGICAL SOCIETY BULLETIN 99 
make special studies of it, that a means of com- 
bating the pest was discovered. It is now known 
that the protozoan imbeds itself in the epithelial 
layer of the skin of its host, and after feeding 
on the tissues for a few days, drops to the bot- 
tom; and that it has two modes of reproduction 
—by fission and by spore formation. On reach- 
ing a certain stage it either divides and forms 
new protozoans in situ or it leaves the fish and 
drops to the bottom, where it undergoes encyst- 
ment and develops spores to the number of per- 
haps a thousand. ‘These make their escape in 
three or four days and seek a host. Their de- 
velopment is more rapid in warm than in cool 
water. 
As there is nothing that can be used to reach 
the parasites while imbedded in the skin of 
the host, they must be killed during the unat- 
tached stage, which can be accomplished with 
solutions quite harmless to the fish. 
Dr. Stiles’ early experiments showed that in 
an aquarium at least four feet deep and supplied 
with a free current of flowing water, the plac- 
ing of salt on the bottom of the tank, which 
would leave a layer of fresh water at the top 
and various stages of salinity between top and 
bottom, enabled the fish to get rid of its par- 
asites in from one to ten days. The infected 
fishes were observed to dive into the salty areas 
at the bottom of the tank and wallow there 
for an instant before seeking the fresh water 
at the top. All parasites leaving the fish were 
killed on reaching the salty water. 
Dr. Stiles also found that fishes could live 
for some days in very weak solutions of methy- 
len blue and eosin, while parasites leaving the 
fish were killed in a few minutes in such a solu- 
tion. These chemicals are dangerous, however, 
and constant aeration is necessary in employing 
them. Simpler and safer methods for the treat- 
ment of small aquarium fishes are therefore in 
use at present, and the following have been 
found successful. 
Transfer the fishes from one to three times 
daily into fresh water of the same temperature. 
Some aquarists use two jars, leaving the patients 
for eight hours in one and then transferring 
them to the other, taking care to use jars with- 
out plants or pebbles and sterilizing each jar 
as the fishes are removed from it. Two weeks 
of this treatment are said to cure. The water 
in which the fishes are placed, though under 
any circumstances requiring to be changed from 
once to thrice daily, may contain a weak solu- 
tion of salt or a very weak solution of perman- 
ganate of potassium. 
For tropical fishes the same treatment is rec- 
ommended, with the usual advice that a heighten- 
ing of the temperature of the water is always 
beneficial to them, and it may be raised to 90 
degrees for a few hours every day. (This can 
be done by placing an electic bulb in or under 
the tank.) 
The aquarium should be sterilized while the 
fishes are out of it, with a strong salt solution 
(20 percent. ) 
Symptoms—Fishes suffering from this disease 
lose their appetite, appear listless, and tremble 
so much that the disease has been called The 
Shakes. The fins may also appear ragged.* 
Orner Parasites: Crustaceans, Leecues, Evc. 
The fish may be able to rid itself of most gill 
parasites as previously stated, if provided with 
fine sand. External parasites, such as the com- 
mon crustacean, drgulus, called the carp-louse 
because of its great frequency on the scales of 
fishes of the carp family, cannot be removed in 
any way except forcibly. No solution that will 
kill this parasite will not also kill the host. Soft 
brushes are sometimes used to remove the par- 
asite, but less injury to the scales will result 
if the pest is picked off with a slender pair of 
forceps. The fish should be given a salt or 
permanganate bath after the operation, to pre- 
vent bacteria from entering the spots where the 
parasite has been attached. 
Leeches and flukes are usually introduced on 
plants, and if they have once settled in an aquar- 
ium it is best to sterilize the entire tank and 
destroy such plants as are in it, for the leech 
can hide itself most cleverly, and its new-born 
young can hardly be seen at all. 
Ror 
Fix ConGestion ann Tarn 
If blood streaks become noticeable in fins 
and tail, farther trouble may be looked for un- 
less the congestion is arrested at once. It usu- 
ally ends in tail rot, which, if not observed and 
treated in time, makes the fish “of an unhand- 
some look.’’ A thin white line appears along 
the edges of the tail, the diseased sections later 
breaking up and hanging in strings. It is one 
of the ailments most frequently met with in 
*Since this paper went to press, we learn that Mr. 
H. L.. Canfield of the Fairport (Iowa) Fisheries Sta- 
tion has found carbonate of soda an effective remedy 
for Ichthyophthirius in channel catfish. He places 
affected specimens in a bath containing five ounces of 
the soda in each gallon of water, leaving them in until 
they become uneasy. This method kills all but the 
large imbedded parasites, and improvement is 
noticed after six days’ treatment. 
