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, e f 



Pia 298. Setse of different Polychata (after Malmgren and Claparcde). a, Hooked seta of 

 Sdbella crassicornis ; b, of Terebella Danielsseni; c, seta with spiral ridge from Sthenelais ; 

 d, lance-shaped seta of Phyllochcetopterus ; e, of Sabella crassicornis ; f, of Sabella pavonis ; 

 g, Composite sickle-shaped seta of Nereis cultrifera. 



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 wanting, the 

 setae are 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- 



fiG 2'JO Anterior end of Polynoe extenuata, the first . 



elytron on the left hand being removed (after Cla- sent in great number, 



parede). The two setae of the oral segment are visible ; go fa^ t] ie integument 

 .El, Elytra. . , 



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 



