DESCRIPTION OF PLATES I-XV 



LIST OF REFERENCE LETTERS 



A.B.S. . 

 Acic. 

 Bl.V. . 

 Br. 1 . 

 Ch.SegS 



D. . . . 

 D.V. . 

 Ep.. . 

 Gon. 

 Gon.V.. 

 H. . . 

 M. . . 

 M.Circ., 



M.Long. 

 M.Gr. . 

 Mo. . 

 N.C. . 

 Neur . 

 Neur. 1 . 

 N.O. . 



N.O. 1 . 



Not. . 

 Not. 1 . 

 Not.Pr., 



Not.Eetr. 

 Not.S. . 

 Nph. 1 . 



, Achaetous body-segment. 

 . Aciculnm. 



Blood-vessel. 



First gill. 



First chaetiferous seg- 

 ment. 

 , Diatom (as statolith). 



Dorsal blood-vessel. 



Epideraiis. 



Gonad. 

 . Gonadial blood-vessel. 



Heart. 



Muscle-band. 



^Circular and longitudinal 

 / muscles of body-wall. 



Metastomial groove. 



Mouth. 



Nerve-cord. 

 , Neuropodium. 



First neuropodium. 



External opening of ne- 



phridium. 

 , External opening of first 



nephridium. 

 , Notopodium. 



First notopodium. 

 ^Protractor and retractor 

 / muscles of notopodium. 



Notopodial chaetal sac. 

 , First nephridium. 



Nph.F.D. 

 NpJi.F.V. 

 N.Sh. . 



N.St. . 

 Nuc. Gr. 

 (E. . . 

 (E.Conn. 

 CE.Gl. . 

 P. . . 

 Per. . 

 Prost., 



or Pr. 

 8 1 , S 2 , S 3 



S.P. . 

 S.P.O. . 



St. . . 

 Sth. . 

 St.O. . 



Stom. . 

 St.T. . 



Tent. . 

 Ves. 



Dorsal lip of nephridia 



funnel. 

 Ventral lip of nephridial 



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. 

 Statocyst. 

 Stomach. 

 Opening of statocyst to 



exterior. 

 Stomodaeum. 

 Tube from statocj'st to 



exterior. 

 Tentacle. 

 Vesicle, or bladder, of 



nephridium. 



PLATE I. 



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

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



Fig. 1. 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. 



