^^ THE NEW EVOLUTION 



P notochord extending forward in front of the nerve cord; 

 no skull; no true brain 



Cephalochorda 

 k? notochord not extending the full length of the body; body not 

 segmented 

 l^ notochord confined to the anterior portion of the body; body 

 with three divisions, the proboscis, the collar and the 

 trunk 

 m^ elongated and worm-like; collar not produced; alimen- 

 tary canal a straight tube; without asexual reproduc- 

 tion; free living, inhabiting burrows in sand or mud 



Balanoglossida 



m 



body not worm-like; collar region produced into one or 

 more pairs of tentaculiferous arms; alimentary canal 

 U-shaped; reproducing asexually by budding; inhabit- 

 ing tubes secreted by the animals themselves 



Cephalodiscida 

 P notochord confined to the hinder portion of the body, and 

 usually absent in adults 



TuNICATA 



y^ no true notochord; nervous system ventral, 

 and not hollow; no lateral openings 

 from the pharynx to the exterior 

 h} unsegmented; no chitinous bristles or setas on the body 



P- no ventral foot, mantle-fold or shell; mouth associated with 



a series of hollow ciliated tentacles arranged in a circle, 



horseshoe, double horseshoe or double spiral; no special 



sense organs; elongated and worm-like 



nz^ perivisceral cavity divided into three intercommunicating 



chambers; no horny structures on anterior portion of 



body; inhabiting tubes secreted by themselves and 



covered with foreign materials 



Phoronidea 

 m^ body cavity very large and undivided; anterior protrusible 

 portion of body often covered with rows of horny 

 hooks or with small imbricating scale-like papillae 



SiPUNCULOIDEA 



P with a ventral foot, and usually a mantle-fold, and a uni- 

 valve or bivalve shell; no hollow ciliated tentacles about 

 the mouth, which is commonly provided with very 



