PISCES 



471 



mullet, and conger-eel. A taenioid scolex constantly infests 

 the muscles and viscera of the great sunfish. The tetrarhynchs 

 differ from one another as regards the form of 

 their proboscides and the relative number and 

 disposition of the hooks. I must refer to my 

 ' Bntozoa ' for a full description, with figures, 

 of a larval tetrarhynch from the wall of the 

 intestine of a haddock. Some Tetrarhynchi 

 exhibit a very complex armature, as may be 

 seen in Tetrarliynchus longicollis infesting the 

 tope or penny dog-fish (Galeus vulgaris}. In 

 this species the hooks are uniform in size, 

 and arranged in spirally disposed circles car- 

 rying from twenty to thirty hooks each. In 

 the tetrarhynch from the whiting the hooks 

 show much irregularity both as regards size 

 and arrangement. A remarkable scolex in- 

 fests the sun-fish (Orthagoriscus mola) ; it is 

 a true tetrarhynch, but has been variously 

 classed. According to my view all the follow- 

 ing titles refer to this parasite : Gymnorhyn- 

 chus reptans, Eudolphi ; G. horridus, John 

 Goodsir ; Acanthorhynchus reptans, Diesing ; Bothriorhynchus 

 continuus, Van Lidth de Jeude ; Bothriocephalus patulus, 

 Leuckart ; Acanthocephalus elongatus, Rudolphi ; A. macrourus, 

 Bremser ; Floriceps saccatus, Cuvier ; F. elongatus, Blainville ; 

 Scolex gigas, Cuvier ; Tetrarhynchus reptans, Cobbold. 



Five or six examples of the sunfish have been examined by 

 me in the fresh state, all of them being infested by tetra- 

 rhynchs. In the fish here drawn (fig. 82) the liver and lateral 

 muscles were extensively tunnelled by the parasite. In all 

 instances the anterior part of the worm was found surrounded 

 by a thick, clear, transparent cyst, which gradually diminished 

 in thickness towards the tail. When liberated from its investing 

 capsule the head of the worm presents a quadrilateral figure, 

 each lateral half being furnished with a bipartite facet. The 

 retractile boring organs are club-shaped, each supporting about 

 1600 hooks. Nearly all the hooks display a uniform length and 

 thickness, but at the lower part of each proboscis there are 

 two conspicuous circles, the hooks of which are at least twice 

 as large as the others. The joints of the immature strobile are 

 well formed, but exhibit no trace of sexual organs. If it be 



G. 81. -Portion of the 

 proboscis of a scolex 

 of Tetrarhynchus infest- 

 ing Merlangus vulgaris. 

 Magnified. After Busk. 



