FISH PARASITES COLLECTED AT WOODS HOLE. 
297 
Cysts with Trematode Ova. 
[Plate 40, figs. 82-84, IT. S. N. M. No. 0523.] 
Throe specimens of white perch ( Moron e amcricana), examined on August 27, had the viscera 
generally covered with pigment patches. A study of these not only verified observations of a similar 
nature published by me in vol. xx, Proceedings of U. S. National Museum, page 537, but confirmed 
certain conclusions reached with regard to some waxy masses found in a diseased ovary of this fish. 
In the specimens ova were found (1) with cyst just beginning; (2) with thick cyst of connective 
tissue; (3) cyst and ovum both surrounded with a waxy secretion, but ovum still plainly visible; 
(4) a waxy mass similar in appearance to (3) but with no ovum visible; (5) masses of very dark-brown, 
almost black, pigment. The ova were not of uniform size; the largest, however, measured 0.020 mm. 
and 0.013 mm. in the two principal diameters shown in optical section. 
Sections of the liver were made, but no pathological features were noted further than presence 
of ova in pigment patches, of which there were a large number in the serous coat of the liver. 100 ova 
were estimated in a single section through one of these pigment patches, which would indicate 
approximately 4,000 ova in the pigment patch. 
Gasterostomum ovatum Lt. 
[Monostomum orbiculare Ruilolplii, Linton, Proc. XT. S. N. M., vol. XX, pp. 541-542, I 1 ] . LTV, figs. 2-5, XT. S. N. M. No. 4872.] 
The specimens from Lobotes surinamevsis, referred by mo to the genus Monostomum, belong to the 
genus Gasterostomum. As they appear to be new, I propose the name Gasterostomum ovatum for the 
species, and give the following emended definition: 
Body ovate, depressed, flattened ventrally, convex dorsally. Acetabulum subterminal a little 
broader than long. Mouth [fig. 3, ph., loc. cit. ] at about anterior fourth of body. The mouth is easily 
overlooked. When a specimen is placed in a transparent medium a snbglobular pharynx is seen, in 
appearance like a small ventral sucker. Vitellaria arranged in a somewhat semicircular band between 
the mouth and acetabulum along the right side as far as the first testis, and along half the length of 
the left side. Testes two, snbglobular on the right side back of the mouth, and one following the 
other closely. Ovary globular in front of testes and beside the mouth. Uterus voluminous, crowded 
with small, nearly globular ova, its folds lying along the left side and midventral lino from a point a 
little in front of the mouth to near the posterior end, where there is a large roundish mass of ova, 
which in ventral view usually obscures the oblong ovate cirrus pouch. The latter lies near the 
mid-ventral line, its base on a level with the posterior edge of posterior testis. The external genital 
aperture is at the posterior end. 
Additional measurements, in millimeters: Length 1.91, greatest breadth (at mouth) 0.92; length 
of acetabulum 0.17, breadth of same 0.2; breadth of mouth 0.07; diameter of oral sucker (pharynx of 
original description) 0.14; length of anterior testis 0.25, breadth of same 0.21; length of posterior 
testis 0.21, breadth of same 0.25; diameter of ovary 0.17; diameter of ova, (average) about 0.017; 
distance between acetabulum and mouth (centers) 0.56. 
Gasterostomum arcuatum sp. nov. 
[Plate 41, figs. 85-90, XT. S. N. M. No. 6524.] 
On two occasions small trematodes were found in the bonito ( Sarda sarda ) — July 20 numerous, 
August 8 few — in pyloric c:cca and intestine. In the living worm the color of the lateral margins is 
translucent white, anterior yellowish white, posterior yellowish brown where the ova show through 
the body wall; neck very changeable, contracting and extending incessantly. These prove to belong 
to the genus Gasterostomum. 
The following description is based on preserved specimens: Body slender, cylindrical, tapering 
gracefully to anterior end, arcuate; posterior end bluntly rounded, covered with minute, low, fiat 
spines, which are dense in front and throughout the greater part of tlio length of the body; anterior 
sucker terminal with circular aperture; ventral sucker (mouth) situated little in advance of middle, 
smaller than anterior sucker, globular ; aperture subcircular ; intestine short, soon expanding into a 
