368 



ANNELIDA. 



The form of the movable setae varies extremely, and affords a good 

 character for the classification of families and genera. According 

 to the strength, form, and mode of ending (fig. 298), the following 



a, lie d e } * m 3 



Fis 298. Sette of different PolycHoeta (after Malmgreu and Claparede). a, Hooked seta of 

 Salclla crassicornii ; I, of Terebella Danielsseni; c, seta witb spiral ridge from Sthenelaix ; 

 d, lance-shaped seta of Phylloch&topterus ; e, of Stibella crassicornis ; f, of Sabella pavonis ; 

 g, Composite sickle-shaped seta of Nereis cuUrifera. 



forms can be distinguished : hair-setae, hooked-setae, flat-setae (palece), 

 lance-setae, sickle-shaped setae, etc. When the parapodia and their 



appendages are com- 

 pletely 

 setae are 



wanting, 



FIG. 21)9. Anterior end of Polynoe cxtenuata, the first 

 elytron on the left hand being removed (after Cla- 

 parede). The two setse of the oral segment are visible ; 

 SI, Elytra. 



the 



embedded in 

 pits in the integument, 

 and are arranged either 

 in one or two rows on 

 either side, that is, in a 

 lateral ventral row on 

 either side, or in a ven- 

 tral row and a dorsal 

 row on either side. In 

 such cases the number 

 of setae is small (Oligo- 

 chceta). The setae may, 

 on the contrary, be pre- 

 sent in great number, 

 so that the integument 



on either side seems to 

 oe covered with long hairs and setae, and a thick felt of hairs 

 shining with a metallic lustre is distributed over the whole dorsal 



