ODONTOSYLLIS FULGURANS. 181 



small, curved, dorsal bristle on the twenty-seventh, the long natatory bristles 

 extended from the twenty-eighth to the fifty-second segment. In another example the 

 sexnal elements and the capillary bristles occurred from the twenty-fifth to the fortieth 

 segment. He found gregarines in the intestine of one ; whilst in another the head was 

 regenerated, but without proboscis or proventriculus. Its phosphorescence is so bright as 

 to show the parts under the microscope. 



The specimen from deep water in St. Magnus Bay showed the structure of the 

 bristles very clearly, and the terminal hook of the distal piece was perhaps a little less 

 curved than in the form from the Channel Islands. 



It would be difficult to frame a theory explanatory of the phosphorescence of this 

 annelid under a littoral ascidian in the Channel Islands, and at the depth of 100 fathoms 

 in the Zetlandic seas, just as it was long ago pointed out how uncertain the theory is 

 which endows, on the one hand, phosphorescent animals with the faculty of alluring others 

 which fall a prey to them, and, on the other, of attracting the attention of some to their 

 own destruction. 



This species has been a favourite subject of study with observers from De la Voie 

 (1666) onwards, the memoirs of Vianelli, Claparede, and Panceri on its phosphorescence 

 being especially noteworthy. The last-named author locates the luminosity in certain 

 glands at the base of and in the dorsal cirri, but other tissues may not be excluded under 

 the influence of the nervous system. The figures of this author are of much interest. 

 Viviani probably refers to this form under his Nereis radiata. 1 Adler, again (1756), gives 

 his Noctiluca marina a round head, two eyes, two tentacles (figure shows three), and a 

 body of twenty segments. It is two lines long, and is found amongst the marine algas. 



The Nereis noctiluca, of 0. F. Miiller 2 (1806) is apparently a female bud of a form 

 approaching this and resembling the coloured figure of a male Autolytus. In the figure 

 of the segments the foot is inverted. He adds " Corpus totum purpurascens." 



It is possible that the Syllis fulgurans of Audouin and Edwards, which was sent to 

 them by Duges from the shores of the Mediterranean, is this species. 



A very closely allied form is the Odonto syllis dugesiana of Claparede, 3 who described 

 it as having nine teeth in its proboscis, but Langerhans 4 has given it only six (as in 

 0. fulgurans), and the compound bristles are similar. 



Claparede 5 shows a young Odonto syllis of three bristled segments and three eyes on 

 each side. The bristles are very long and have tapering terminal pieces. 



Webster found a large adult male with swimming-bristles commencing on the 

 twenty-first segment and extending over forty-two, in Great Egg Harbour, New Jersey. 



Malaquin 6 describes a young Odontosyllis in the dipharyngeal stage with five bristled 

 segments and lateral ciliated pits. 



1 ' Phosphor. Maris/ p. 11, Tab. iii, figs. 5 and 6. 

 3 ' Zool. Dan./ iv, p. 31, Tab. cxlviii, figs. 1—3. 



3 ' Grlanures/ p. 97, pi. viii, fig. 2. 



4 ' Zeifcsch. f. w. Zool./ Bd. xxxii, p. 554, Taf. xxxii, f. 15. 



5 ' Beobacht./ p. 81, Taf. xii, fig. 15, 1863. 



6 Op. cit., p. 429, pi. xiv, fig. 29. 



