POLYMNIA NEBTJLOSA. 129 



in general form, but are readily distinguished by the presence of a second tooth above 

 the main fang and the somewhat shorter base. The posterior incurvation is below the 

 middle, and the process on the anterior outline is prominent. 



Reproduction. — This species, according to Lo Bianco (1909), is ripe in spring. 

 Southern found it mature from February to May. 



The tube is fragile, covered with grains of sand and small stones. 



Malmgren thought that Terebella lutea from the Mediterranean was allied, yet 

 distinct. Moreover, he considered that T. clebilis and T. nebulosa, Grube, should form 

 a distinct genus (Polymnia,), since their branchiae and hooks are so characteristic. 



De St. Joseph (1894) found in this species Gregarines pertaining to the genus 

 Polyrabdina, Mangazzini, 1 also Gregarina terebellde, Kolliker, and encysted Distomes 

 of the same kind as in Nicolea venustula and Polymnia nebulosa. 



Examples of Polymnia have been found by Orton 2 (1914) to attain a good size in 

 much less than a year, so that their development is somewhat rapid. 



A variety, of small size, procured at various parts of the British coast, at first 

 sight resembling Malmgren' s P. arctica, shows finer divisions of the branchial filaments, 

 which are proportionally long. Two teeth as a rule are present in the hooks above 

 the main fang, a trace of a process occurs midway along the curve below the latter, and 

 the ventral outline (of the base) is more convex. 



2. Polymnia nebulosa, Montagu, 1818. Plate CXIV, fig. 6— body; Plate CXXVa, 



figs. 3 and 3 a — bristles and hook. 



Specific Characters. — Cephalic region with a large collar or upper arch, at the 

 junction of which with the body posteriorly is a dense series of eye-specks, whilst it 

 has a frilled inward curve at each lower edge. The upper arch folds inward to form 

 the upper lip. Tentacles pale orange and spotted with white. Below the mouth is 

 a transversely elongated tongue-like fold, and then the lower lip extends to the dorsal 

 fold on each side. Body 70 — 100 or more mm. in length, as thick as a man's little 

 finger, and having ninety or more segments, soft in consistence, fragile, of the typical 

 shape, tapering posteriorly and ending in an anus with a crenate margin. Segments 

 two-ringed. Orange-red, sometimes inclining to brown or paler and speckled all over 

 with white. First segment massive ventrally ; second, third and fourth with small 

 lamellas. Ventral shields fourteen or fifteen, the anterior narrow and broad, the posterior 

 wider and shorter from side to side. Seventeen pairs of bristle-bundles. Segments in 

 a line with the second and third branchige have a free lamella. The tentacles have the 

 same hue as the body. Branchias three, on segments 2, 3 and 4, the first the largest, 

 sub-dichotomously divided, the terminal processes numerous so as to give the organs 

 a dense arbuscular aspect, or like a corymb. Nephridia from the third to the eighth 

 segment. Setigerous processes with two sets of bristles, long, minutely striated forms 

 with curved, tapering and winged tips, and a shorter series with translucent tapering 



1 ' Atti Acad. Lincei/ 4 e ser., t. vii, p. 229, 1891 ; see also Schneider, ' Arch. Zool. Exper./ t. iv, 

 1875, p. 598, pi. xxii, figs. 85 and 86. 



2 c Journ. M. B. A.,' vol. x, p. 316. 



186 



