SYLLIDJE. 141 



The proboscis seems incapable of retraction, and the parasites do not move after removal 

 from the host. The Syllid is colourless, except the posterior part of the gut, which is 

 grey, has four very minute eyes, very long tentacles, and uniramous feet." 



Syllids have, moreover, long been celebrated for their phosphorescence. Thus 

 Viviani 1 (1805) mentions and figures no less than three, viz. Nereis cirrhigera (Odontosyllis 

 fulgurans ?), Nereis mucronata, and Nereis radiata. The British forms are as conspicuous 

 in this respect as the foreign, one of the commonest (Eusyllis tubifex, Grosse) causing 

 striking manifestations of the phenomenon from its vast abundance on the blades of 

 tangles covered by Obelia. 



In this country the pelagic types chiefly belong to the genus Autolytus, but in foreign 

 waters certain of the Syllids proper likewise appear to have a pelagic stage. Thus when 

 Mr. Crossland was in the Pearl Fisheries' steamer in Mersa Harbour, Durur, he observed 

 numerous "small Heterosyllids circling round on the surface after the manner of 

 Heteronereids. They were rapidly discharging genital products, the water in the jar in 

 which they were placed becoming milky in a minute or two. They were readily killed by 

 adding a drop of spirit to the water, and under this treatment showed a brilliant green 

 phosphorescence. The dorsum was marked with alternate oblique and transverse bands 

 composed of minute dots. The dorsal cirri were slender and the ventral cirrus absent. 

 Long swimming-bristles occurred superiorly, and the terminal pieces of the compound 

 bristles were simple." 



Andrews 2 also observed the adults of Autolytus prolifer swimming at the surface of 

 the sea in the evening. 



The relationships of the remarkable pelagic types found by Greef 3 off the Canaries, 

 such as Pontodora and Pelagobia, cannot be accurately determined, though he was 

 inclined to link them to the Syllidao. In general form and in the structure of the 

 alimentary canal, nervous system, and bristles, they certainly appear to approach that 

 family and the Hesionidse. 



The Syllids abound between tide-marks, under stones, amongst zoophytes, algas, 

 shells, and sponges. In the laminarian region they frequent oyster-banks, mussel-beds, 

 or occur in great numbers amongst zoophytes on the blades of the tangles. 



They are especially common in the Mediterranean and at Madeira (Langerhans), yet 

 the colder British area is not far behind the more genial southern waters in the variety of 

 the species which frequent it. Thus Langerhans thought the waters of Madeira 

 surpassingly rich with forty species, yet our own waters hold nearly the same number, 

 and, whilst a few may prove to be varieties of one form, others not included may be 

 discovered by future investigators. 



They range to a considerable depth (600 to 1380 fathoms). 



Little was done by the early naturalists to assign a definite place to the Syllidse. 

 Savigny made them the twelfth genus of his Nereids, and his description is fairly 

 accurate for the period. 



Grube, in his ' Familien der Anneliden' (1851), gave order to the group, but he 



1 f Phosphorescentia Maris/ G-enuas, 1805, p. 11, tab. iii, figs. 1 — 6. 



2 < Journ. Morph./ 1892, p. 186. 



3 ' Zeitsch. f. w. Zool./ Bd. xxxii, pp. 245 and 247, taf. xiv (1879). 



