COMPLETE HARTMAN: POLYCHAETES FROM CALIFORNIA 117 



Flabelligera commensalis Moore, 1909 

 Frontispiece 



Flabelligera commensalis Moore, 1909a, pp. 286-288, pi. 9, figs. 62, 63. 

 Flabelligera haerens Chamberlin, 1919, p. 16. 



Collections. Southern California, in intertidal rocky areas (many) ; 

 in shelf depths associated with Chaetopterus variopedatus (many). 



This beautiful bristle-cage worm is sometimes to be found on the 

 surface of the common purple urchin, Strongylocentrotus purpuratus 

 (Stimpson) where it takes on the color of the host species. Length in life 

 is 20 to 45 mm. There is no mucus sheath covering the body. Colors in 

 life were noted by Anker Petersen, who also prepared the colored plate : 



Everted head light buff; sides of body lightly touched with reddish 

 purple ; under side of body dull orange-yellow with faint tinge of green. 

 Alimentary tract showing through body wall is bright orange to brick 

 red ; this is followed posteriorly by an undertone of yellowish green. 



Immature specimens, or those not associated with urchins, are grayish 

 or brownish with an undertone of green, due to the color of the blood ; 

 larger individuals tend to be flecked with purple, or red. The oral 

 tentacles are of a single kind, all slender and filiform ; they number 50 

 or more on a side and are inserted on a rounded membrane above the 

 prostomial lobe. This membrane is medially prolonged as a slender, 

 smooth tongue. Each tentacle is cylindrical, has transverse rows of cilia 

 and may be capable of considerable movement. In specimens from 

 urchins, the tentacles are purple, the same color as the body. The paired 

 palpi are pale to nearly white, thick, inserted at the sides and below the 

 prostomium. The prostomium is a small, conical lobe with 4 very large 

 eyes in trapezoidal arrangement ; they cover most of the prostomial sur- 

 face. 



The surface of the body is closely covered with short papillae. Similar, 

 but longer papillae cover the parapodial lobes; they have a slender stalk 

 and terminate distally in an elongate inflated lobe. 



Neuropodia are ventrolateral in anterior and median segments, and 

 ventral in posterior segments. They are provided with single dark, distally 

 curved composite hooks. Each pair has the curved ends directed medially. 

 Notopodia have fascicles of slenderer setae ; they are pale yellow in color 

 and less easily seen than the falcigers because they are largely concealed 

 by the long parapodial papillae. Flabelligera haerens Chamberlin (1919) 

 from kelp holdfasts, refers to the free-living stage of F. commensalis. 



