7//. AXNELIDA: CII^JiTOPODA. 



311 



somite.s, which contain the sexual organs, develop special bristles and para- 

 podia (fig. 2y4, ^1). Thus many species of Nerds pass into the ' Hetero- 

 ■iiereis ^ stixge. In other Polychfetes the sexual part (epitoke) separates 

 from the sexless atoke portion and swims freely, while the atoke produces 

 new epitokes. In the Samoan Islands Eunice viridls reproduces in this 

 way, the epitokes corning to the surface at certain times in incredible 

 numbers, forming the ' palolo worm,' a delicacy in the Samoan diet. In 

 still other species the epitoke regenerates the head and thus becomes an 

 independent generation, fiyllis and HeterosylUs are thus related. The 

 Autolytidce furnish the most complication. Here the atoke, by budding 

 as in Mijrianida, tig. 279) forms chains of dimorphic individuals which 

 later separate. The individuals of male chains were formerly described as 

 ' Polt/bost7'ic]ius,' the females as ' iSacconereis.^ This same homonymy ex- 

 jilains the regenerative powers of many worms. Thus if certain eartli- 

 worms be cut in two, they will continue to live and will reproduce the lost 

 parts. 



Another important character of tho C'ha'topoda is the posses- 

 sion of bristles or cha^^ie. These arise in special follicles, singly 

 or several in a bunch, of which usually there are four — right and 

 left, dorsal or lateral and ventral — in each somite. Each follicle 

 (fig. 280) is a sac of epithelium opening on the surface and having 

 at the base a special cell for the development of each bristle. The 

 developed bristles project from the follicle and, moved by appro- 



FiG. 2S0.— Arrangement nf a bristle in an Olik'oelisete. (After Vejdowski.) c, epithe- 

 lium: rnuUi), circular and lon^^itudinal muscles; *;(, muscle of the foUieie; h^ 

 ciia'ta ff)llicle, its cliieta in function; h-^, follicle for replacement, the formative 

 cell at its base. 



priate muscles, form small levers of use in locomotion. Their 

 numbers, shape, and support are of much systematic importance. 



Order I. Polychsetee. 



The Polych»ta3 owe their name to the fact that each group of 

 bristles contains many chaetae; but more important is that the 



