292 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Sections of both the large and the small specimens were made, and while it does not enter into 
the plan of this paper to give histological details, the following anatomical details may he here 
recorded for purposes of identification : The cuticle is thick, particularly its inner layer, which 
presents a crenulate outline. Both longitudinal and circular muscles strongly developed, especially 
the former, and in the neck transverse fibers are very abundant. The submuscular cell layer is very 
conspicuous. The pharynx is about half the length of the oral sucker, and opens into the intestinal 
rami by a very short oesophagus. The acetabulum is strongly developed, and evidently functions as 
a powerful suctorial organ. In all the specimens sectioned it had drawn in a part of the tissues con- 
stituting the ventral portion of the base of the neck, while the cavity of the acetabulum contained 
material which appeared to be pieces of the intestinal mucous membrane of tho host. The branches 
of the intestine lie dorso-laterally, and reach to the posterior end of the body. On account of the state 
of contraction of tho body, the intostinal walls are much convoluted. The cells lining the intestine 
are large and the ends turned toward tho lumen are swollen and stain very slightly with carmine. 
The excretory vessels were traced forward to the oral sucker and back to the posterior end, where 
they unite. The vessels are large, their walls thin, granular inner surface staining deeply with 
carmine. Near the posterior end the walls become somewhat thickened and appear much folded. 
Tho ovary is in front of testes, toward the dorsal side and close behind tho acetabulum. Some of the 
sections indicate an obscurely lobed structure. Tho shell gland lies on the ventral side of tho ovary 
and immediately behind the acetabulum. The uterus, beginning at the shell gland just behind the 
acetabulum, fills the posterior part of the adult body with its voluminous folds. It leads forward on 
the dorsal side of the acetabulum, and in front of that organ passes ventrally beside the cirrus pouch, 
the external genital aperture being on the ventral side of the neck, a little to the right of tho median 
line in one specimen, a little to tho left in another, and, as near as could be determined in these highly 
contracted specimens, approximately about the anterior third of distance between the two suckers. 
The testes are two, laterally placed behind the ovary and ventrally, and near enough so that some 
of the transverse thin sections of the body passed through both the testes and the ovary. 
The seminal vesicle lies immediately in front of the acetabulum. It is inclosed in a spherical 
muscular sac, but it and tho vas deferens, cirrus, and prostate gland all are inclosed in a special sac. 
This is partly shown in the sketch, fig. 49, p. sv. No posterior seminal receptacle was made out. 
The vitelline glands are conspicuous voluminous organs lying laterally and posteriorly rather 
more ventral than dorsal. They appear to consist of numerous branching glands which extend 
forward to the posterior edge of tho acetabulum. In sections stained lightly with carmine these organs 
are beautifully differentiated as golden-brown bodies with parts stained red with the carmine. Both 
ovary and testes stain strongly in carmine. 
Bistomum pyriforme sp. nov. 
[Plate 38, figs. 52-59, U. S. N. M. No. 6510.] 
These distoma were found on four occasions, August 10, 19, 22, 25, in enormous numbers in the 
pyloric c;eca of the rudder-fish (Palinurichthys perciformis). 
Body very slightly compressed, of various shapes, but usually elliptical or pyriform in outline, 
armed with low, Hat, rounded, scale-like spines. Neck in some slightly extended; in others the oral 
sucker was retracted (fig. 56). Mouth subterminal, orbicular. When the worm is extended so as to 
give a favorable view tho oral sucker is slightly elongated and separated from the pharynx by a short 
oesophagus. The latter, of course, is difficult to make out in contracted specimens. Acetabulum a little 
broader than long, about equaling the oral sucker and situated about the middle of the length of the 
body. Intestinal branches conspicuous, straight, reaching to the posterior end of the body. Testes 
two, nearly globular, but breadth slightly greater than length in elongated and considerably greater 
in contracted specimens, situated well toward the posterior end, close together, one immediately in 
front of the other. Cirrus pouch elongated, on right side of acetabulum opening in front of the 
same; cirrus sx>inose. Ovary small, round, situated in front of the testes near the seminal vesicle, 
dorsal, and a little toward the right and close to the acetabulum. Vitellaria voluminous, filling the 
greater part of the body, especially at the posterior end and along the lateral margins as far forward 
as the acetabulum. Uterus evidently short, ova very few and relatively large, lying between ovary 
and acetabulum and equaling in length the diameter of that organ. 
