DESCETPTION OF PLATES I XV 



LIST OF REFERENCE LETTERS 



Dorsal lip of ncphridia 



fitnnel. 

 Ventral lip of nepluidial 



funnel. 

 Nervous sheath of stato- 



cyst. 

 Nerve to statocyst. 

 Nuchal groove. 

 Oesophagus. 

 Oesophageal connective. 

 Oesophageal gland. 

 Pit (possibly sensory). 

 Peristomium. 



[Prostomium. 



First, second and third 



septa. 

 Septal pouch. 

 Opening of septal pouch 



into coelom. 

 Statoc^-st. 

 Stomach. 

 Opening of statocyst to 



exterior. 

 Stomodaeum. 

 Tube from statocyst to 



exterior. 

 Tentacle. 

 Vesicle, or bladder, of 



nephridium. 



PL.\TE I. 



Arenicola marina (Linnaeus). Light- and dark-coloured examples, taken, at 

 the same time, from the beach at Musselburgh, Firth of Forth. 



Fig. \. — A typical light-coloured example. The buccal mass and pharynx are 

 protruded. 



Fig. 2. — Anterior end of a similar specimen ; dorsal aspect. 



Fig. 3. — A dark-coloured example. 



Fig. 4. — Anterior end of a similar specimen, with buccal mass and pharynx 

 protruded ; dorsal aspect. 



