334 DR W. CARMICHAEL M'lNTOSH ON THE STRUCTURE OF THE 



he has met with to the uniform arrangement of the stylet-apparatus, as, in 

 addition to the forward position of the lateral stylet-sacs, the central stylet and 

 its surroundings are placed in his second oesophageal cavity — that is, in our 

 reservoir; and his figure* bears out his description, representing, moreover, the 

 organ as placed at the commencement of the posterior channel. The species is 

 easily identified by the position of the lateral stylet-sacs and other peculiarities, 

 and there is certainly no such abnormality of the central apparatus or alteration 

 of type as noted and figured by this naturalist. 



In a very pretty new species — dredged in Lochmaddy — of a salmon hue, 

 striped down the back with two brown and a white central streak, having also a 

 transverse brown bar at the posterior part of the head, and only two eyes,f the 

 stylets were similar in shape to those of 0. melanocephala, but decidedly smaller. 



This shows that while distinctions in size and shape are valuable specifically, 

 they should not be too much relied on. 



The anterior chamber in 0. gracilis (Plate VII. fig. 1) is very short in pro- 

 portion to the great elongation of the animal, the stylet-region being found only 

 a short distance behind the ganglia ; indeed, in this respect, it is not far removed 

 from Polia involute/, Van Beneden. The floor of the anterior chamber has 

 generally a bilobed aspect under examination, and hence differs considerably from 

 that of 0. alba. On each side of the floor in front of the stylet-sacs the end of the 

 proboscis has not the massive muscular structure usually found in this position, 

 but internally has a somewhat opaque mobile lobulated glandular arrangement, 

 which, when the organ is everted, projects as two semi-opaque whitish papillae 

 (one on each side), the stylet-sacs being sometimes prolapsed into their interior. 

 The central stylet and its apparatus do not easily project in this condition. The 

 stylet-region proper, consisting of that part from the floor of the anterior chamber 

 to the border of the reservoir, is somewhat opaque, on account of the glandular 

 nature of the walls anteriorly, and the layer of granular glands posteriorly. The 

 latter are placed far back, and in developing specimens form an opaque granular 

 mass on each side of the ejaculatory duct, sometimes entirely filling up the angle 

 (at a, same fig.), and consist of a dense grouping of minute clear granules, and 

 occasionally coarser particles in lobulated glands, which are apparently homo- 

 logous with the granular glands of other species. The lateral stylet-sacs have 

 very long ducts, and each encloses from seven to ten stylets of a characteristic 

 shape, besides other contents. The central stylet is appended to a basal sac of 

 great length, the sac indeed resembling the outline of some long bone, such as 

 the radius, the stylet being articulated to the head, while the distal extremity of 

 the bone is represented by the swollen posterior end of the sac. The latter has 



* Op. cit. pi. xiii. fig. 8. 



■f The Nareda superba of Stumpson has likewise two eyes, but has no longitudinal stripes. — 

 Synopsis Mar. Invert, of G. Manan. N. Brunswick, p. 28, fig. 17, 1853. 



