FISH PARASITES COLLECTED AT WOODS HOLE. 285 



PART IT. 



Parasitic Copepod from the Squeteague. 

 [Plato 33, figs. 1-5, U. S. N. M. No. 6507.] 



I include in this report notice of a copepod parasite found by Mr. E. E. Tyzzer, July '22, under 

 the skin on the preopercular bone of a squeteague (Cynoscion regctlis). One specimen was given to 

 me on the date of capture and a sketch was made of it while it was still alive. There was a mass of 

 ova associated with the specimen and a few were attached to the forked tail. Later two other smaller 

 specimens were given to me, which had been found in the same iish in the same position, but on the 

 opposite side of the head. The larger, when viewed from above, had the following characters: 



Head bluntly rounded in front, obscurely cordate behind. A single median, orange-colored pig- 

 ment spot, suggesting in position the eye of Cyclops, was distinctly seen in the living specimen, but 

 can not be made out in the alcoholic specimens. One pair of short, obscurely jointed antenna- were 

 seen protruding beyond the anterior border of the head. The body is not clearly articulate, but 

 about eight constrictions of the body-wall impart an articulate appearance. These constrictions 

 divide the body into about eight segments, including the head. There is, then, first the head, whose 

 breadth equals or even slightly exceeds its length; second, a neck-like segment, narrower than the 

 head, cylindrical, the diameter about three-fourths the length; following this the third division of 

 the body, which is ovoid, enlarged, its diameter more than three times the breadth of the head and 

 its length equal to about one-third the entire length of the animal. Behind the enlarged segment are 

 four cylindrical segments diminishing in diameter and slightly also in length posteriorly. The diam- 

 eter of the first segment behind the enlarged part is about one-third the diameter of that part; the 

 last, that is, the eighth segment, is anteriorly cylindrical and posteriorly divides into a forked tail, 

 each fork being equal in length to the combined length of the preceding three segments and standing 

 out at nearly right angles to the axis of the body. 



From certain faint superficial markings on the dorsum of the enlarged portion there is some 

 reason for believing that it stands for at least three primary divisions of the body. On its anterior 

 end, also, there is a faint constriction, indicated in the sketch, which, if it were of equal distinctness 

 with the other constrictions, would make a short segment, not enumerated in the foregoing. One of 

 the smaller specimens when placed in glycerin showed a corresponding constriction in the intestine 

 at this point. The other did not. Moreover, the intestine in it showed annulatious anterior to this 

 which did not have any corresponding annulations in the body-wall. 



The color in life was whitish, the intestine dark-brown in its anterior portion. The alcoholic 

 specimens arc white, slightly tinged with yellow. The exterior wall, moreover, is separated a little 

 from the parts beneath, especially behind the enlarged portion, so as to look like a thin transparent 

 cuticle. The opaque inner part is studded with sharp-pointed elevations, giving a spinose appearance 

 posteriorly (fig. 5). This appearance is presumably due to the shrinking of the inner part away from 

 the outer wall. The latter is thin, transparent, and very little crustaceous. 



On the under side of the head at its anterior end is a circular aperture within which could be 

 distinguished a jointed appendage. This appears to be one, the left, of a pair of maxillae. There 

 appeared to be three joints to this appendage and what was taken to be the basal joint of its fellow. 

 There was some indication of an additional rudimentary pair of appendages in front of these. No 

 anal opening could be made out on the large specimen at first, although a longitudinal mark on the 

 ventral side of last segment, just at the bifurcation, probably represents it. Later it was made out, 

 but was indistinct in the opaque specimen. The two smaller specimens, which were not in first-class 

 condition when they came into my possession, when put in glycerin showed the intestine apparently 

 ending in an anus which was situated on the ventral side of the last segment just at the bifurcation 

 and opening posteriorly. 



Dimensions of large specimen in millimeters : Length 13; length of head 0.76, breadth of head 

 0.78; length of second segment 1, breadth 0.7'2; length of third segment 4.5, breadth 2.5; diameter of 

 fourth segment 1.5, of seventh 1.3; average length of last five segments 1.2; length of antenna 0.21. 



