VERMES. 59 



The systematic position is doubtful of 



Order 3. Chcetognatha. Marine, free-living hermaphrodites with lateral 

 fins, head, cerebral, sub-oesophageal and ventral ganglia. Are entero- 

 ccelic (mesoderm developed from archenteric diverticula). Sagitta ger- 

 manica. S. bipunctata. 



