9:60 Dr. Von Siebold on a Double-bodied Intestinal Worm, 



Trematoda^ but simple and manifold tortuous canals, like 

 those we find in all the ISlematoidea. The testis with its bi- 

 furcate penis, according to its structure, coincides with the 

 male generative organs of the cylindrical worms. Further, 

 the generative organs lying together with the Intestinal canal in 

 one cavity of the body forms another character which belongs 

 to the parasites of the first order. It was only the blind end 

 of the intestinal canal, and the want of rings on the skin, which 

 could cause any difficulty as to its being placed among the 

 Nematoidea; much less its wide mouth, which, as before re- 

 marked, has more resemblance to the basin-like sucker of the 

 Trematoda, yet not formed of a muscular, but of a horny sub- 

 stance. Several species of Strongylus show the same. The 

 two before-mentioned basin-formed mouths may have misled 

 Montagu, as he classed this animal with ihe Fasciola; and 

 having given the mouth as being divided into six parts, Ru- 

 dolphi thought proper to place it by the side of Distomum 

 linea7'c {poro aiitico nodulis sex cincto), as he supposed the 

 male neck with its mouth-opening to be a petiolated porus 

 posticus. Thus considered, this worm could not acquire the 

 interest which properly belongs to it; as at the same time a 

 true double-branched Distomum. could be placed by its side ; I 

 mean Distomum fur catum ^. 



I take leave, in conclusion, to call attention to the following 

 comparisons, which, in the examination of this worm, after 

 having learnt its true structure, forced themselves on me, with- 

 out intending to lay value on them. In all round worms the 

 males are shorter than the females. In Syng. trachealis the 

 male portion is by far much shorter than the female. In the 

 male worms the caudal extremity, where the generative or- 

 gans always terminate, always joins at the pairing-time with 

 the body of the female, forming an acute angle t- Bearing 

 this in mind, we have the following transition to our mon- 

 strous form. Both sexes of almost all cylindrical worms unite 

 only at the pairing-time. The male of the Hedruris andro- 

 jphoraX has the habit at other times also of embracing its 



* Riidolphi, Synopsis, p. 107, No. 72j and Bremser, IconeSy tab. ix. 

 figg.13,14. 



■j- See in Bremser, Icones^ tab. iii. figg. 8, 15; and Giirlt, Lehrbuch der 

 Patholog. Anatomie der Haus-Saitgethiere, tab. vi. fig. 35. 



X Nitzsch, in Ersch and Gruber's Encyclopaedia, Th. vi. p. 49, and Th. 

 ix., 3rd taf., fig. 7; hIso in Schmal, Tahulce Jnatomiam JEntozoorum i/lustr., 

 tab. xvii., fig. 5. Nitzsch observed (p. 49,) at the margin of the caudal 

 socket of the female, a small arm which he thought to be the undeveloped 

 tail end. I have satisfied myself that this arm is of a horny nature, and that, 

 as it enters into the ir)embrane of the stomach, it serves as a firm hold for 

 the female worm. The place on which the animal fixes itself is also per- 

 ceivable on the outer side of the stomach by a tuberculous projection. 



