746 REPORT OP COMMISSIONER OF FISH AND FISHERIES. [28] 



5. Dibothrium plicatum, Kudolphi. 



[PI. in, Figs. 1-6.] 



Eclilnorlujnchiis xipJiiw, Gmeliu, Syst. Nat., 3047. Zeder, Naturg., 162. Ru- 

 dolpbi, Eutoz. Hist., II, W8. 



Botliriocephalus pUcatus, Rudolpbi, Syuops. 136 and 470, PI. in. 2. Bremser, 

 Icon., PI. xm, 1 ami 2. Creplin, Nov. Obs. 87,JP1. 11, 12-14; Erscb. and 

 Grub. Eucycl., xxxn, 297. Dujardin, Hist. Nat. des Helm., 614. Van 

 Beueden, Meni. Acad. Belgique, xxxvin, 36. Olssou, Lund's Uuivers, 

 Arsskrift iv, 11, PJ. in. Fig. 66. Von Linstow Comp., Helm., 218. 



Bothriocephalus iruncatus, Leuckart, Zool. Brucbst., I, 37, PI. I, 13. 



Dibothrium plicatum, Rudolpbi, Diesing, Syst. Helm., i, 591; Revis., Cepb. 

 Par. 243. Wagener, Nov. Act. Nat. Cur., xxiv, Suppl. 71, PI. vm, 94, 95, 



This Dibothrium is peculiar tothecommon sword-fish (Xipliiasgladius}, 

 having never yet been found in any other host. Following is the 

 description given of it by Diesing: 



Head sagittate, compressed truncate at tbe apex, witb oblong, lateral botbria. 

 Neck long, soinewbat terete, swollen at tbe base, segments very sbort, at lengtb 

 longer, witb tbe posterior margin crisp-undulate. 



I have referred to this species five specimens of Dibothria from the 

 rectum of Xipliias gladius. The head and neck of each of these para- 

 sites were completely buried in the walls of the rectum. The part thus 

 buried measured about 13 lniu . The cavity in which the head and neck 

 were inclosed was, in each case, an enlarged cyst-like space filled with 

 transparent, watery lymph. These,spaces were noticed on the outside 

 of the rectum, lying immediately under the serous membrane, and were 

 at first taken to be encysted larval cestods, but upon cutting into one 

 of them the inclosed head and neck, except in one case, to be noticed 

 further on, were observed to be attached firmly to the inner muscular 

 layer of the rectum. After cutting away the remaining tissue from the 

 enclosed necks they were found to be continuous with the bodies of 

 some large Dibothria which lay in the lumen of the rectum and were 

 attached to its walls. The color of the head and neck was bluish- 

 white, that of the body grayish-yellow. After removal from their host 

 the worms were placed in sea- water, where they at once contracted to 

 about one-half their former length, while, at the same time, they be- 

 came much broader and thicker, with the segments so crowded together 

 that only their posterior edges were visible. They then had assumed 

 the characteristic shape and appearance which is shown in the sketch 

 (Fig. 1). Before they had thus contracted they bore a close resem- 

 blance to D. manubriforme (U. S. Fish Commission Keport for 1886, 

 pp. 456-458, PI. i, Figs. 1-4). The length of one after thus contracting, 

 exclusive of the head and neck, was 54 mm , while its greatest breadth 

 was l^ mm . Another measured 66 mm in leugth, with a breadth of 7 mm 

 throughout nearly its whole length, narrowing abruptly, however, at 

 the last three or four posterior segments, which measured 2 mm in 

 breadth. 



