296 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Distomum sp. 
[Plate 39, fig. 72 ; Plato 40, figs. 73-75.] 
Among the numerous small distoma found during the summer of 1898, 1 note briefly a form found 
on two occasions, but as only a single specimen was obtained in each case formal identification has 
not been attempted. Both are characterized by having the body armed with minute, scalc-lihe spines, 
dense on the neck, but becoming sparse posteriorly on the body. One was obtained from a scup 
(Stenotomus cltri/sops) August 15, the other from a flounder ( Paraliclitliys dentatus) August 25. Since 
the stomach of the latter contained several small scup, and the distomum was obtained by washing 
out the alimentary canal of the flounder, the true host of the worm is quite probably the scup. 
Dimensions of living specimens, in millimeters: 
(1) Specimen from scup: Length 0.62, greatest breadth 0.31, diameter of oral sucker 0.09, of 
acetabulum 0.09, longer diameter of ova 0.076, shorter diameter of same 0.034. 
(2) [U.S.N.M., No. 6521.] Specimen from flounder: Length 1, greatest breadth 0.53, diameter of 
oral sucker 0.18, of acetabulum 0.18, longer diameters of ova 0.076, shorter diameter of same 0.052. 
The same specimen mounted in balsam is 1.22 in length and an ovum measured 0.064 and 0.034 in the 
two principal diameters. 
Diagnostic characters, so far as they can be made out from the latter specimen, are as follows: 
Body ovato, depressed, whitish in life, covered with short sealelike spines becoming sparsely scattered 
posteriorly; neck short with tendency to bo constricted behind oral sucker; mouth subterminal; 
acetabulum equaling or slightly exceeding mouth; pharynx longer than broad; 0 ‘Sophagus none; 
branches of intestine, simple, spacious, extending to near posterior end; testes two, median, back 
of middle of body, close together, relatively large, broader than long; genital aperture in front of 
acetabalum, a little to the loft, cirrus pouch behind acetabulum ; ovary subglobular lying immediately 
in front of anterior testis; uterine folds, containing a few (6) relatively large ova, lying between the 
ovary and acetabulum; vitellaria along lateral margins from the posterior end to acetabulum. 
Immature Distoma encysted in skin of Cunner. 
[Plato 40, fig. 76-81, U. S. N. M. No. 6522.] 
A cunner ( Tautogolabrus adspersus) was examined September 5, in which the general surface of 
the body, including the fins, was covered with minute cysts. The appearance of tho fish agreed in 
minutest detail with Ryder’s description of a similar case observed by him (Bulletin U. S. Fish Com- 
mission for 1884, pages 37-42). Black pigment colls are very abundant in tho vicinity of tho cysts, 
where they make black, opaque masses immediately surrounding tho cysts. Pigment is almost entirely 
absent from the exterior surface of tho cyst where tho epidermis is tightly stretched. The cysts them- 
selves are nearly transparent. This is true for tho larger cysts. The smaller cysts have pigment 
colls ovor their surface, but in no groator abundance than normal. As tho cysts grow, the pigment 
cells retreat from the surface and accumulate about the periphery of tho cysts as it is seen in optical 
section when a scale with these cysts is put under a cover glass and examined with aid of a microscope. 
The red pigment of tho skin continues to be represented ovor surface of cysts longer than the black. 
In all cysts observed pigment cells wore absent from surface just above the young worm. 
Ryder thought those cysts were due to the presenco of the cercaria of sometrematode. He does 
not appear actually to have seen them. Some of the young removed from tho cysts proved to be 
young distoma, thus confirming tho general conclusion of Ryder. 
Sections woro made of the fins containing numerous cysts, but without throwing any light on 
the probable identity of the adult species represented by these immature forms. The Avails of these 
cysts, as seen in section, prove to be relatively thick. In one which measured 0.32 by 0.25 mm. in the 
two principal diameters tho wall of the cyst Avas 0.05 mm. thick. 
The following table gives tho dimensions, in millimeters, of living specimens removed from cysts : 
Measurements. 
No. 1. 
No. 2. 
No. 3. 
0. 70 
0. 82 
0. 47 
0. 17 
0. 20 
0. 17 
0. 00 
0. 05 
0. 05 
0. 048 
0. 04 
0. 041 
0. 035 
0. 024 
0. 021 
0. 045 
Diameter of a single cyst, 0.36, not including the surrounding pigment. 
