TBTEARHYNCHID7E. 137 



activity to gain access to its ultimate host. This is particularly 

 the case with a remarkable form of parasite infesting the sun-fish 

 (Orthagoriscus mola) — a worm which has been described over and 

 over again by observers, each author imparting to the species either 

 a new specific or generic name. It is, generically, a true tetra- 

 rhynch, but has seldom, if ever, been regarded as such by previous 

 entozoological writers.* 



Of the five or six examples of the sunfish which I have either 

 had an opportunity of inspecting or dissecting in the fresh state, 

 all of them, if I recollect rightly, were infested by the tetrarhynch in 

 question. The fish here figured was a particularly small one ; never- 

 theless, the liver and great lateral muscles were extensively tunneled 

 by the parasite in question (Plate X., Fig. l).t In all cases the 

 anterior part of the worm is invested by a thick, clear, transparent 

 cyst which closely invests the animal, but gradually diminishes in 

 thickness towards the tail. At this part it can be traced in the 

 tissues of the host for a considerable distance beyond the caudal 

 extremity of the entozoon, forming a thin cord which serves to 

 indicate the track previously taken by the wandering scolex. It is 

 doubtful if any one ha? ever succeeded in tracing the cord to the 

 point of the parasite's original departure, i.e., from the spot where 

 the animal became transformed fi:'om the condition of an embryo into 

 the characteristic scolex state. The earliest conditions of the scolex, 

 of the embryo (proscolex), and of the mature proglottis, are, I beheve, 

 at present unknown to science, but it is more than likely that the 



* Synonyma: — Gymnorhynchus reptans, Eudolphi ; = G. horridus, John Goodsir ; = 

 Jcanthorhynchus reptans, Diesing ; = Bothriorhynchus continuus, Van Lidth de Jeude ; 

 ^^ Bothriocephaliis patulus, Leuckart ; ^= Anthocephalus elongatus, Rudolphi; = A. ma- 

 crourus, Bremser ; = Floriceps saccatus, Ciivier ; = F. elongatus, Blainville ; = Scolex 

 gigas, Cuvier ; = Tetrarhynchus reptans, Cobbold. 



t It was captured off Anstruther on the coast of Fife, September 6th, 1856. The 

 dimensions were as follows : — Length from head to tail, 18 inches ; between tips of dorsal 

 and anal fins, 26 inches ; depth of body, 12 inches ; length of pectorals, 2\ inches ; 

 width of gill aperture, 1 inch. Several other individuals were taken in the Fii-th of 

 Forth a few weeks previously. The larger specimens were infested with other forms of 

 entozoa, in addition to the ectoparasitic trematode helminth known as the Tristoma 

 coccineiim of Rudolphi. 



