116 



F. W. GAMBLE, M.SC, AND J. H. ASHWORTH, B.SC. 





Habitat. 



Colour. 



Gills. 



Breeding 





Adult. 



Young. 



Season 



"Shore lugs," 

 or littoral 



variety, 6 — 8" 

 long, excep- 

 tionally 10" 



" Worms," or 



Laminarian 



variety, 



8—15" in 



length. 



Thesandy and muddy 

 shores of bays, estu- 

 aries, and harbours, 

 extending from high 

 water mark to and 

 sometimes beyond 

 low tide level 

 Burrow U-shaped 



The sandy shore ex- 

 posed at extreme low 

 spring tides, occa- 

 sionally extending 

 above this 



Burrow a vertical 

 shaft 



Greenish 



brown or 



reddish 



black 



Black or 



very dark 



brown 



Semi- 

 transpa- 

 rent, yel- 

 lowish or 

 brown 



Dark red, 

 opaque 



Moderately 



developed 



Branches 



with 3 — 5 



pairs of 



gill-plumes 



Very well 



developed. 



Branches 



with usually 



about 12 



pairs of di- 



chotomous- 



ly arranged 



plumes 



July, 



August 



January 

 to May. 



2. The cilia lining the central or gastric region of the alimentary canal 

 are specially arranged (1) on the sides of a ventral groove which is con- 

 tinued to the anus, and (2) on curved shallow grooves running down- 

 wards and backwards into the former. The current caused by the 

 action of these cilia carries a stream of mucus and of digested food 

 slowly backwards and away from contact with the mass of sand in the 

 gut. As these grooves are in close connection with parts of the visceral 

 plexus, absorption may take place from them. 



While the ventral groove is morphologically equivalent to the 

 similar structure of Oligognatlms (described by Spengel 1 ), and probably 

 to the " siphon " of Capitellids, we have seen no reason for regarding it 

 or any other part of the alimentary canal as " respiratory " in function. 



3. In the circulatory system the two hearts each contain a cardiac 

 body. This structure is composed of masses of granula and vacuolated 

 cells, projecting into the cavity of each ventricle. Functionally they 

 may be regarded as glandular valves preventing the reflux of blood 

 into the gastric sinuses. While previously unknown in Arenico/a, the 

 "cardiac body" has been long known in allied genera (Ophelia, 

 Trophonia, Chlorhsema), but as an unpaired structure in the dorsal 

 vessel (Schaeppi, 1894). Hence, though histologically similar, it is 



" Oligognathus Bonellipe," 'Mitt. Zool. Stat. Neapel,' hi., 1882. 



