of a new Parasitic Worm. 411 



(fig. 3,f) arises, and having formed numerous convolutions 

 around the sigmoid stomachal dilatation above noticed, ter- 

 minates in a kind of ventral fissure, near the point where the 

 leaflets become rudimentary before their change of form is 

 completed. 



Now, as to the true nature and relationships of this little 

 parasite much might be said. Though at first agreeing 

 with Dr. Dobson that it represented a new order of Annelids, 

 I am at present more disposed to look upon it as a new type 

 of worm whose alliance is rather with the Nematoda. 



Though minute scaly spines are often found equally distri- 

 buted over the integument of the body in the Helminths, there is 

 no case on record of a complete series of appendages running 

 on each side through nearly the whole length of the body as 

 in the form above described. In an EchinorhyncJius which I 

 found in the rectum of a Bonito, there were six pairs of simple 

 stout spinous processes attached to the fore part of the body. 

 Something similar may be said of Strongylus horridus, found 

 by Rudolphi in the oesophagus of the water-hen. Other 

 instances might be quoted ; but such organs have always 

 hitherto been found on limited portions of the body. 



It should be remarked also that, just as in the case of the 

 hooklets of the Acanthocephati, the leaflets and stylets of the 

 present form are not supplied with special muscles, in which 

 particular they differ from the sclerous organs of the true 

 Annelida. 



In the following paper Dr. G. E. Dobson has added some 

 further notes on the systematic position of this worm and on 

 the circumstances attending its discovery. 



EXPLANATION OF PLATE XXI. 



a, mouth ; b, oesophagus ; c, intestine ; d, anus ; e, ovarium ; f, oviduct j 

 g, vulva. — N.B. The same letters apply to all the figures. 



Fig. 1. Head and fore part of the body of the worm described above, as 

 seen with a J-inch objective. 



Fig. 2. Exhibits the transformation of the leaflets into the stylets which 

 succeed them. 



Fig. 3. Part of the body, showing the sigmoid stomachal dilatation of 

 the alimentary canal, part of the ovarium, the convoluted ovi- 

 duct, and the lateral appendages. 



Fig. 4. Posterior extremity of the body, showing ovarian sacculi and 

 the termination of the intestine in the anal opening. 



Fig. 5. One of the leaflets, magnified 300 diameters — to show its pecu- 

 liar form and the supporting chitinous fibres spread out between 

 its dorsal and ventral layers. 



Figs. 6, 7. Two stylets, showing the coalescence of the fibres seen in 

 fig. 5, so as to form a pointed process with a bifid base. 



Fig. 8. A single ovum, showing the coiled-up embryo within. 



Fig. 9. Homogeneous placental matrix in which the ova are developed. 



29* 



