322 Dr. Johnston^s Contributions to the British Fauna, 



very minute black spines on their inferior aspect. Branchice 

 naked, not retractile, small, of a milk white colour, placed one 

 on each side of the second ^^ ^^ segment: they consist of two 

 pectinate diverging branches \U uniting to form a tube, which 

 being of a darker colour and firm consistence, is seen run- 



ning obliquely downwards to join a large vessel, which will be 

 described below. The little processes are about seven in number 

 on each branch, and appear to be tubular. The margins of the 

 ventral surface of the rings are thickened, and set transversely 

 with numerous minute black springs, which are excellent sub- 

 stitutes for feet. Anus large, protuberant, roughened with minute 

 dark spines, not terminal, but placed on the under surface of the 

 last segment. This is terminated by two large ovate suckers^ placed 

 on the dorsal margin : their rim is of a dark brown, and sur- 

 rounded with a beautiful fringe of delicate ciliae, which, how- 

 ever, it is difl&cult always to detect. The disc of each sucker 

 seems to be divided into three lesser concavities. 



The transparency of the animal allows us to examine, to a 

 certain extent, its internal structure, which, I think, is very 

 curious, and somewhat anomalous. What I have called the 

 mandibular apparatus^ being of a black colour, is very evident. 

 This is a horny piece placed within the proboscis or gullet, pro- 

 longed in front into two long and slender mandibles, bifid at 

 their apices, which appear at the mouth just below the papillary 

 eminences ; and divided behind into four equal sharp processes, 

 which embrace the gullet on all sides. The animal is constantly 

 extending and retracting the mouth, and this apparatus is moved 

 backwards and forwards accordingly, but it is never protruded 

 beyond the aperture. The mouth is lengthened, not by an evo- 

 lution of a proboscis, as in some of the other Jnnelides, similar to 

 the evolution of the tentacula of a snail, but by the mere exten- 

 sion of the anterior segments; when extended, however, they do 

 form a kind of proboscis, and it is only when extended that the 

 parts can be properly examined. The intestine is not distinctly 

 perceptible, but from what is seen, and as a fine blunt probe may 

 be passed from the anus to the mouth without much derangement 

 to the structure of the animal, we may infer that it is a straight 



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