Figure 1.

Scheme of Lineus body organization. The different body regions (R) along the A-P axis are numbered starting from the anterior end and are characterized by the following structures: R1, cephalic glands, rhynchodeum, and eyes; R2, cerebral ganglia; R3, sensory cerebral organs; R4, postcerebral, preesophageal connective tissue; R5, mouth; R6, posterior esophagus and nephridia; R7, anterior intestine (gonads absent); R8, middle and posterior intestine plus gonads; R9, anus; R10, caudal end.