410 Dr. J. D. Macdonald on the Anatomy 



tion and zoological relationships, giving enlarged figures of 

 the different regions of the body and some structural parti- 

 culars of interest. 



The general form of the body is terete, with a tendency to 

 coil upon itself ventrally, gradually diminishing in size towards 

 the head, which is very small, and preserving a degree of 

 fulness towards the posterior extremity, which is rounded, 

 but slightly truncated. 



The mouth is simple and subterminal in front ; and there is 

 a little cervical constriction marking off the head. 



The cephalo-somatic appendages spoken of by Dr. Dobson 

 are lamellate at the fore part of the body (PL XXI. figs. 1, 5) 

 and styliform (figs. 2, 3, 6, 7) in the rest of its extent. 



The leaflets consist of a simple extension of the integument, 

 broadly sickle-shaped, with the point directed backwards 

 (fig. 5). They are supported by an internal fan-like disposi- 

 tion of chitinous fibres, dividing at the attached extremity 

 into a dorsal and a ventral layer, so as to rest broadly upon the 

 muscular sheath of the body, though having no distinct con- 

 nexion with it. They gradually increase in size from the 

 head backwards (fig. 1) to near the generative opening (fig. 2), 

 where they begin to grow smaller, and become quite rudi- 

 mentary, while the chitinous fibres approximate and coalesce 

 into a pointed bundle with a bilobed base. 



From this point backwards, the leaflets having been trans- 

 formed into pointed styles, these organs grow larger, until 

 they nearly equal the original length of the leaflets. 



There is no external or internal indication of annulose 

 segmentation of the body, if we except the disposition of the 

 lateral appendages, which flank the ventral surface on either 

 side at pretty equal distances. 



The muscular sheath of the body is well defined, and chiefly 

 made up of longitudinal fibres, circular ones, though un- 

 doubtedly present, not being very easily demonstrated. 



From the mouth (fig. 1, a) the intestine passes backwards 

 as a simple straight tube (b) for some distance (about one 

 fourth from the head), where it forms a sigmoid ventral 

 flexure, somewhat dilated, which is surrounded by the convo- 

 lutions of the ovarian tube (fig. 3,/'). It next again takes 

 a comparatively straight course for a little way, and then 

 winds spirally round the spiral rachis of the ovarium, and 

 finally terminates in a subterminal and ventral anus within a 

 kind of sheath (fig. 4, d) . 



The ovarium (figs.3&4,e) consists of a spiral rachis, already 

 mentioned, giving off large rounded sacculi or lobules ; and 

 from near the fore part of the organ a lengthy oviduct 





