POLYCH^TA SEDENTARTA OF THE FIRTH OF FORTH. 641 



Genus Leucodore, Johnston. 



Leucodore ciliata, Johnst., Mag. Zool. and Bot., ii. p. 57. 

 Polydora, Bosc, Histoire Nat. cles Vers, Paris, An. x. 



Branchial cirri confined to middle of the body, absent at either extremity; 

 tentacles shorter than in Spio ; first four somites behind the buccal, bearing 

 acicular setae only; in 5th somite the dorsal setae are much elongated uncini, 

 only the points projecting beyond the skin ; branchial cirri present on seg- 

 ments following the 5th, first being very small; an infundibuliform membrane, 



incomplete dorsally, surrounds the anus. 



'.. 



Leucodore ciliata, Johnston. 



Leucodore ciliata, Johnston, loc. cit.; Malmgren, Ann. Polych. 

 Leucodore ciliatus, Johnston, Cat. Brit. Mus., p. 205. 

 Polydora ciliata, M'lntosh, Fauna, St Andrews, p. 127. 



Specific Characters. — Those of the genus. 



Habits. — This worm inhabits soft mud tubes which are not very firmly con- 

 structed, and which fill up narrow chinks and clefts in rocks. In some oysters 

 which were kept in the summer of 1886 in floating cages in Granton Quarry, 

 and which became coated with sediment, large numbers of this worm were 

 found between the projecting edges of the shell laminae, the end of the tubes 

 often projecting some distance. It is stated by Huxley that Leucodore 

 ciliatus bores holes in the oyster shells. We have not found this to be the 

 case ; the tubes of the worm did not actually pierce the shell in any case, 

 and we have not observed them on oysters newly dredged from the middle of 

 the Firth. 



Anatomy. — The nerve cords are rather wide apart and there is no neural 

 canal. 



Claparede (Chetopodes du Golfe de Naples, 1868) describes in, Leucodore 

 Agassizii, a glandular sac beneath the base of each branchia in somites 

 posterior to the 5th (the modified one). He also describes the nephridium as 

 arising from an internal aperture beneath this sac, turning then in the next 

 somite towards the lateral border of the body, then reflected on itself, and 

 passing to open to the exterior near the dorsal median line. In Leucodore 

 ciliatus we have made out by compression both the glandular sac and the 

 nephridium. 



The nephridium is easily distinguished in the living worm after compression 

 by the black granular matter contained in its cells. This matter is doubtless 

 composed of urinary concretions. The glandular sac is derived from the 

 epidermis. 



