158 DR. T. S. COBBOLD ON ENTOZOA. 



In the Haddock and others of the Cod-family we meet with many kinds of Entozoa 

 and the worms foimd in one species seem liable to occur in aU members of the group. 

 Most of the Trematoda infesting fishes are exceedingly minute, and it is absolutely neces- 

 sary for their identification that specific descriptions should be accompanied with accurate 

 figures. I am led to this remark from the difficulty of making out the identity of a 

 Distoma found associated with Echmorhynchus acus, R., and Jiothriocephalus rugosua, R., 

 in the intestinO' of a Haddock. The trematode in question agrees in some respects with 

 D. scabrum and D. appendiculatum, especially the latter, but difi'ers in a few essentials ; 

 moreover, D. appendiculatum is not mentioned as infesting the Gadidse. Provisionally 

 therefore I propose to regard it as a distinct species, and shall briefly describe it under 

 the title of 2). rachion {payjtaiuc), as follows (figs. 9, 10) : — Body of a faint pink colour; 

 length 3 lines ; flat, covered with min ute spines ; obtuse at either extremity ; posterior 

 half of the body rather broader than the front ; oral sucker large, not quite terminal ; 

 ventral sucker comparatively small, near the centre of the body; oesophagus narrow, 

 twisted, bifiu'cating immediately above the ventral sucker ; gastric canals very capacious ; 

 genital pore large and conspicuous ; internal seminal vesicle, uterine tube, ovary, testes, 

 and contractile vesicle particularly distinct. Some other details in regard to the struc- 

 ture of this trematode will be found indicated in the explanation of the accompanying 

 figures. In regard to Bothriocephahis rngosus I have only to observe, that in conse- 

 quence of the head being found in aU instances fii-mly rooted within one of the pancreatic 

 caeca, it was impossible to ascertain the precise form of the cephalic segment. Dujardin 

 remarks the same peculiarity in specimens obtained by him from Gadus pollachius and 

 G. merlucius. The single Echinorhynchus, obtained from the same Haddock, exhibited 

 when aUve an organ lying near the proboscideal sheath — the so-called lemniscus, con- 

 cerning the use of which we are still ignorant. In common with others, I have observed, 

 in another acauthocephalous species, two of these organs, one on each side of the sheath. 

 They have no connexion with the retractor muscles ; but the latter, in the example under 

 consideration, could not be recognized through the semi-opake integument. A Haddock 

 examined by me on the 8th of May, 1854, contained, in addition to two specimens of the 

 above-mentioned Bothriocephalus, several small cysts enclosing FilaricB, and a larger 

 solitary cyst occupied by a Tetrarhynchtis (figs. 11 to 19 inclusive). These require a 

 passing notice. The minute sacs were imbedded in the submucous tissue of the aliment- 

 ary canal, and scarcely exceeded half a line in breadth. The single large cyst, situated 

 beneath the peritoneum outside the intestine, measured about a quarter of an inch long, 

 and one-eighth of an inch broad. It was oval, semitransparent throughout, and on divi- 

 sion of the peritoneal investment, easily removed. When detached, the fibro-ceUular in- 

 vesting capsule or ectocyst offered a pyriform outline, and from its narrow extremity there 

 proceeded a stalk-like prolongation. The ectocyst on being torn open disclosed the tetra- 

 rhynchoid Scolex, the head and body of which were invagiaated, but became reacUly evolved 

 by gentle pressure applied to the bulky caudal vesicle or endocyst. Amplified forty dia- 

 meters, the internal structures were well seen, the proboscidiform tentacula and " sclerous 

 particles" being especially conspicuous. I have here, with due consideration, applied the 

 term " sclerous" to the subcutaneous corpuscles so abundant in the caudal vesicle, in 



