PARASITES OF FISHES OF THE WOODS HOLE REGION. 
449 
Decapterus macarellus, Mackerel ficad. 
FOOD. 
Only young specimens, 5 inches and under, have been examined. Copepods found in alimentary 
canals of most of them; annelids were found in one lot along with copepods; about 200 fish examined 
in July and August, 1899 and 1900. 
CESTODES. 
1. Cestode larva. Intestines. [PI. xx, fig. 228, «-<?.] 
Shaped something like a spool, with flaring sharp-edged flanges, but changing its shape in a 
remarkable manner, and its length from 1 to 4 mm. September 1, 1900. 
2. Larval cestodes (Scolex poly morphus Dujardin). Small. Free in intestine. See 4 , pp. 789-792. 
Found in eight out of nine lots examined. Two red spots in neck and a single costa on the bothria 
in specimens collected September 1, 1900. 
3. Rhynchobothrium (?). Immature larvae in cysts on viscera. July 31, 1899. 
4. Tetrarliynchus bisulcatus Linton. Cyst on viscera. [PI. xxi, fig. 243.] 
A single scolex, collected iVugust 18, 1900, resembles this species, except that the hooks are 
rather more slender. The borders of the bothria were provided with a band of very minute, dense, 
bristle-like spines. Calcareous bodies unusually abundant, mostly oblong-elliptical in outline and 
uniformly distributed in the parenchyma; largest 0.024 mm. in principal diameter. Diameter of 
proboscis, including hooks, 0.06 mm.; without hooks, 0.034 mm. Length of hooks, 0.024 mm. 
TKEMATODES. 
5. Distomum appendiculatum Rudolphi. Intestine. [PI. xxvm, figs. 312-314.] See 7 , p. 289, pi. 
xxxvi, figs. 25, 26. July 31 and Aug. 2, 1899. Aug. 18 and 22, 1900; few. 
These distomes were very active, and when stretched to their extreme length became almost 
filiform, except in the vicinity of the suckers. As these worms contract very much when they are placed 
in the killing fluid, unless kept compressed, but little idea of their appearance in life can be gained from 
a study of alcoholic specimens. One of these distomes taken August 22, 1900, revealed a structure 
of the vitellaria, which suggested I), monticellii. It was one of the smaller distomes of the lot and 
differed in general appearance from the larger principally in the absence of ova (see figs. 313 and 314). 
The dimensions of the ova in these distomes differ from those which I have recorded for I). appendi- 
cidatum in my report for 1898 [ 7 , p. 289], Dimensions in millimeters, life: Length 2.47; diameter of 
oral sucker 0.15, of ventral 0.35; ova, 0.014 and 0.01 in the two principal diameters. 
6. Distomum vittellosum Linton. See 7 , p. 290. Aug. 2, 1899; Aug. 29, 1900. 
Two distomes on former date and one on latter, with prominent acetabula, belong to the species 
referred to in this paper under this specific name. The one taken August 29 was compared with 
specimens from a young blue-fish taken on the same day, while the worms were alive, and found to 
agree specifically. 
Trachurops crumenophthalmus, Big-eyed Scad. 
FOOD. 
Two small specimens examined August 15, 1899, had in the alimentary tracts the jaws, spines, 
and other fragments of annelids. 
NEMATODES. 
1. Immature (Ascaris). Encapsuled. 
TKEMATODES. 
2. Distomum appendiculatum Rudolphi. See 7 , p. 289, pi. xxxvi, figs. 25, 26. 
This is a small specimen. Length, in alcohol, 0.65 mm.; diameter, 0.26 mm. It appears to 
belong to the species recorded in this paper as D. appendiculatum. 
F. C. B. 1899—29 
