360 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
beneat/' the eye, a cluster of live cysts in front and at the base of the right pectoral fin, 
two at bhe base and in front of the left pectoral fin, one on the back at the posterior 
edge of the base of the dorsal on the right side, and another smaller one a little in 
front of this one, one on the left side near the anterior edge of the base of the dorsal, 
two at the base of the right ventral, a cluster of five at the base of the anal fin mainly 
on the right side, a corrugated mass made up of several cysts on the right side at the 
base of the caudal fin. This mass is 5 by 7 millimetres in its two diameters and the 
epidermis over its lower half is dark-colored. On the left side there is a smaller mass 
at the base of the caudal fin. It is more deeply immersed in the tissues of the host 
than the other. The epidermis of this fish is marked in several places with dark 
purplish blotches. 
Each of the three fishes is in fair condition. When a cyst was broken open a 
milky fluid escaped and the wall of the cyst collapsed. A small quantity of the fluid 
contents when subjected to microscopic examination revealed the presence of myriads 
of psorosperms. These are somewhat top-shaped, one end broadly rounded and 
slightly flattened, the other tapering to a point. Their dimensions are about as 
follows: Length 0.017 millimetre, breadth 0.01 millimetre, thickness 0.006 millimetre. 
The outline presented by the edge differs from a side view only in being a little nar- 
rower. There is, however, a low ridge on the margin, which may be seen when an 
individual is turned on its edge, but which is not visible as such in a side view. A 
cross section of one at its thickest part would be a broad ellipse. They are trans- 
parent, or nearly so. The walls are thick and strong, and resist the action of both 
sulphuric acid and caustic potash for a long time. They do not exhibit any tendency 
to change their shape or capacity with either of the above reagents or with glycerine 
or acetic acid. The protoplasmic contents of these thick- walled cells appear, in most 
cases, to be evenly and finely granular. I was unable to distinguish anything corre- 
sponding to the twinned vesicles or polar capsules characteristic of these problematical 
organisms, although the specimens when placed in caustic j)Otash or sulphuric acid 
become quite transparent and the thick walls are sharply defined. Specimens which 
were left for several days in dilute sulphuric acid showed no sign of disintegration. 
The protoplasmic contents, however, had disappeared or were represented by a few 
granular bodies. What appeared to be a median transverse partition was made out 
in many individuals in lateral view. An ill defined mass near the smaller end was 
present in many (made visible when treated with caustic potash) which may be the 
beginning of the polar vesicle. No evidence of protractile threads was found. 
A cyst was stained with BeaPs ammonia carmine, mounted in paraffine, and cut 
into sections. The cyst was allowed to remain in the staining fluid for several days. 
The walls of the cyst and a granular protoplasmic material within were deeply stained. 
The psorosperms were not in the least affected by the staining material. The wall of 
the cyst is composed of connective tissue, is rather thin, and indistinguishable from 
the deeper layers of the dermis. All the cysts lay immediately beneath the skin. 
Scales appeared to be absent from the surface of the cyst in most cases, although a 
few were observed quite loosely attached ou one of the larger clusters. Numerous 
pigment x)atches are scattered over the surface of the cysts. The sections showed the 
cyst to be packed with psorosperms and with granular protoplasm, the latter for the 
most part lying near the wall of the cyst. There is no apparent order of arrangement 
