LVLi 



CCELIIELMIXTIIES 



Order I. Polychaette. 

 The Polvcha-ta? owe their name to the fact tliat each group of bristles 

 contains many chxtx; but more important is that the liristk^s of each side 



are supported l)v a lleshv outgrowth of the 

 somite, the parapoJiiiDi, in whieli two por- 

 tioits corresponding to the bunches of 

 bristh'S — dorsal, iiolopoiiiiiiii: \'entral, iniiro- 

 podiiiJii — may be recogni/ed (fig. -54). 

 This is the I'lrst appearance of true appen- 

 dages, but they chifer from those of Arthro- 

 poda in iiot being joiitted to the body nor 

 jointed in themsehes. On the dorsal sur- 

 face may occur chverse outgrowths, known, 

 according to position or function, as cirri, 

 elvtra, gills, etc. ; on the head, palpi and 

 tentacles. The cirri are long processes on the parapodia, and like palpi 

 are tactile (fig. 254). Elytra are thin lamelki: wliich cover tire back like 



shingles and thus protect the 

 liody (kg. 2O2). 



Nearly all Polychates are dioe- 

 cious and undergo a more or less 

 pronounced metamorphosis; with 

 few exce[itions (Ma)ivinikia'^ from 

 the Schuylkill, .V(7-(/,';* in California) 

 they are marine. 1 liev arc usually 



■"^ss^ 



Fig. 260. — Head with ]iro- 

 truded pharynx of A'tft/.j 

 vcrsipcdatj (after Ehler.s). c, 

 cirri, k, jaws; I, head with eyes; 

 p, palpi; t, tentacles. 



Fic. 262. 



Fig. 261. — Ampliiln'lt- onnilii* (from \"errill). 



l'"ic.. 262. — Head of Polynoc spinijcra (aflcr I'.hlersk Hack eiilirely covered with 

 el\'tra; cirri and parapodia projecting at tlic sides. 



divided aeeordini:; to their habits into fi.xed (Sedenlaria) and free forms (Er- 

 rantia). 'I'he Sedenlaria feeil on vegelcdile mallei", usually form leathery 



