THE PHYLA ASCHELMINTHES AND NEMERTEA 



221 



II. Gastrotricha. Aquatic microscopic animals with ventral por- 

 tions ot the epidermis ciliated, with posterior adhesive tubes 

 and with a nematode-like pharynx. 



III. Kinorhyncha. Marine microscopic animals with a segmented 

 cuticle and a spiny head that can be withdrawn into the body. 



IV. Nematoda. Tapered cylindrical worms with a triradiate pharynx, 

 a modified excretory system, and a very heavy cuticle covering 

 the body. 



^ Rotifera. GastrotricHa KinorhynctiSt 

 (f^ioating ±yp^) (head wit: 



0or'd.iaveea- 



Nexna.i>o<ia. 



Aca.TitKocepliala 

 .{head evertre<^ 



Figure 12.1. Classes of the phylum Aschelminthes. These are considereid to 

 separate phyla by many authors. Redrawn from Hyman. 



be 



