S\XLIDAE. 163 



Syllidae. 



The members of this family have usually a definitely segmented thread- 

 like body ; commonly, but not always, with tentacles and cirri strongly articu- 

 lated or moniliform, and often long. 



The prostomium bearing a pair of palpi in varying degrees of separation, 

 three tentacles, and usually two pairs of eyes, or more rarely three, and even four 

 pairs, of small size. 



Peristomium usually bearing one or two pairs of tentacular cirri, these 

 rarely absent; in some with setae. 



Other somites with parapodia in most uniramous, a notopodial branch, 

 however, appearing at sexual maturity in a certain number of genera. Dorsal 

 and ventral cirri usually present, but may be lacking. 



Setae both simple and composite, of varying forms, or rarely only simple 

 setae occurring. 



Pygidium with a single pair of cirri and sometimes with a short median 

 process. 



Proboscis typically showing an anterior chitinous region and a posterior 

 muscular one; bearing at the anterior end a series of soft papillae and either 

 unarmed or, more commonly, bearing one or more teeth. 



The syllids in the complexities of their reproduction are remarkable. 

 Schizogamy is frequent and of great variety.^ In direct reproduction, or epigamy, 

 the syllids present phenomena wholly comparable to those so long known among 

 certain nereids, which at sexual maturity undergo marked transformations, 

 giving in Nereis the Heteronereis phase. As in the nereids the transformation 

 to the epitokous phase is manifested principally in an increased development of 

 the sensory organs and in the development of accessory locomotor apparatus 

 in the posterior region of the body. 



The members of this family are, with rare exceptions, of small size and are 

 often more or less transparent. Phosphorescence has long been known in the 

 group. 



They live ordinarily in the immediate vicinity of the shore, abounding 

 between tide-marks under stones and shells, and especially among Algae, 

 hydroids, and bryozoans. They occur as commensals in sponges and ascidians, 



' Cj. especially the monograph by Malaquin, Recherches sur les syllidiens, 1893. 

 Also, St. Joseph, Les annelides polychetes des cotes de Dinard, Ann. sci. nat. Zool., 1887, ser. 

 7, 1. Vigiiier, Etudes sur les animaux inf^rieur de la Raie d'Alger, Arch, zool. exper., 1884, ser. 2, 2. 

 Johnson, Biol. bull. 1906, 2; Amer. nat., 1902, 36. 



